NEWS
January 28th, 2017
New Fermat factor from FermatSearch!
3370842847 . 2^{3058}+1 is a Factor of
F_{3056}!!!
Gary Gostin found this new Fermat factor using his GMPbased pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E78890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his first factor of the year!

December 19th, 2016
New Fermat factor from FermatSearch!
9659599821 . 2^{2125}+1 is a Factor of
F_{2123}!!!
Gary Gostin found this new Fermat factor using his GMPbased pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E78890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his fifth factor of the year, the seventh factor this year!

December 5th, 2016
New Fermat factor from FermatSearch!
26778342591 . 2^{1683}+1 is a Factor of
F_{1680}!!!
Gary Gostin found this new Fermat factor using his GMPbased pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E78890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for his fourth factor of the year, the sixth factor this year!

December 1st, 2016
Productivity pages cleanup on FermatSearch!
Gary Gostin and
Roman Maznichenko offered ther executables for Linux and Windows/CUDA
and some benchmark: our productivity table reflects the new timings, now normalized towards.an Intel core i5 3.0 Ghz CPU
A very big thank you, folks!

November 30th, 2016
A brand new program for Fermat factoring has been released!
Gary Gostin offered his own program
pmfs available for others to use it.
pmfs version 3.0 is a program written by Gary Gostin. It is a Linux x8664 executable that calls the GMP library
and can use multiple processor cores to improve performance.
The zip file includes documentation, a benchmarking results spreadsheet, and a Linux tar file
containing the pmfs executable and example input and output files.
pmfs performs better than GMPFermat for N > 800/1000 and on multiple core (up to 240) environments.
Look for it on the
download page.
Thank you Gary!

November 28th, 2016
New Fermat factor from FermatSearch!
8662575142599 . 2^{289}+1 is a Factor of
F_{287}!!!
Roman Maznichenko found this new Fermat factor using his CUDAbased Feromant program running on a GTX580 (factoring) + 1 core Intel (Skylake) i56600K@4000GHz (sieve)
Feromant_CUDA was compiled under Win64 and CUDA 7.0.
It is worth noting that this is the third divisor for F
_{287}!
Congratulations to Roman from FermatSearch, for the fifth factor of the year!

October 30th, 2016
New Fermat factor from FermatSearch!
58951871175 . 2^{1299}+1 is a Factor of
F_{1296}!!!
Gary Gostin found this new Fermat factor using his GMPbased pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E78890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the fourth factor of the year!

September 23rd, 2016
GMPFermat code updated!
Mark Rodenkirch graciously offered an update of his program
GMPFermat.
Version 2.5 uses fast, optimized assembly routines and fixed a small bug.
Thank you Mark!

August 29th, 2016
A Desperate appeal!! by Richard K. Guy
At the time of my 80th birthday, when John Conway and I were writing The Book of Numbers, John bet that there would be no
further complete factorizations of Fermat numbers in the next 20 years. I bet him $20.00 that there would be. Now that my 100th
birthday is only 3 years away, I'm beginning to get a bit worried!
I'll even go so far as to split the $20.00 with anyone who completely factors F12 or F13 or any larger Fermat number!!
(Note: The actual deadline is September 30, 2016; please compare UPINT, 3rd edition, page 16.)
Nearly three years have passed, and it looks like Professor Guy's $20 is doomed.
There are two methods to try to find factors of Fermat numbers. One is sort of the equivalent of trial factoring.
This site and the FermatSearch subforum has details for reserving ranges.
The other method is ECM testing, using mprime/Prime95.
F12 is now at the stage where ECM testing is looking for factors in the range of about 65 digits (about 215 bits).
Each curve takes about 3.1 hours on a 2.3 GHz Haswell architecture.
F13 is now at the stage where ECM testing is looking for factors in the range of about 60 digits (about 200 bits).
Each curve takes about 1.7 hours on a 2.3 GHz Haswell architecture.
Finding a new factor would be interesting in its own right, albeit rather improbable since you might have
to run tens of thousands of curves or even hundreds of thousands before you hit a factor at this level,
if one even exists. And even then, saving Professor Guy from financial ruin would require the cofactor to be prime as well.
Nevertheless, in case anyone wants to make a token effort, here are some lines you could add
to your worktodo.txt (requires stopping the program first, or to avoid having to do that,
just create a worktodo.add file that the program will automatically read and append to worktodo.txt
the next time it does a disk write).
There are 10 curves for F12 (2^{4096}+1) and 18 curves for F13 (2^{8192}+1),
so maybe 30 hours of CPU time for each on a modern Haswell machine.
F12 needs 535MB of memory in stage two, and F13 needs 579MB.
ECM2=1,2,4096,1,800000000,80000000000,10,"114689,26017793,63766529,190274191361,1256132134125569,568630647535356955169033410940867804839360742060818433"
ECM2=1,2,8192,1,260000000,26000000000,18,"2710954639361,2663848877152141313,3603109844542291969,319546020820551643220672513"

June 29th, 2016
Tables cleanup on FermatSearch!
Gary Gostin and
Roman Maznichenko volunteered their CPUs and time
to help clean up the older orphaned ranges of the project.
A very big thank you to them!
Meanwhile I am working to add new features to the site, so please stay tuned!

May 25th, 2016
New Fermat factor from FermatSearch!
24142479 . 2^{14590}+1 is a Factor of
F_{14587}!!!
Adolf Nordin found this new Fermat factor usingFermFact and PFGW running on his home system
Congratulations to Adolf from FermatSearch, for the third factor of the year!

April 4th, 2016
New Fermat factor from FermatSearch!
60567741 . 2^{9555}+1 is a Factor of
F_{9552}!!!
Gary Gostin found this new Fermat factor using his GMPbased pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E78890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the second factor of the year!

February 21st, 2016
New Fermat factor from FermatSearch!
118807331 . 2^{7139}+1 is a Factor of
F_{7137}!!!
Gary Gostin found this new Fermat factor using his GMPbased pmfs program running on an HPE Superdome X system
with 240 Ivy Bridge cores (E78890 v2 @ 2.80 GHz).
Congratulations to Gary from FermatSearch, for the first factor of the year!

December 25th, 2015
Merry Christmas with FermatSearch!
21346190509623 . 2^{290}+1 is a Factor of
F_{287}!!!
Roman Maznichenko discovered the sixth factor of the year (and its own sixth factor) just after a month since the last one discovered!
HW: GTX580 (factoring) + 1 core Intel (Haswell) i54670K@4000GHz (sieve).
SW: his own program Feromant_CUDA (compiled under Win64 with CUDA 7.0).
He verified it using Feromant (for CPU).
Congratulations from FermatSerch, Roman, keep the factors coming!

November 25th, 2015
FermatSearch strikes again!
4004779405 . 2^{2288}+1 is a Factor of
F_{2286}!!!
Gary Gostin discovered this using his pmfs program, which uses the GMP library, running on an HPE Integrity Superdome X server.
He verified it using Fermat.exe on his laptop.
Congratulations from FermatSerch, for the fifth factor of the year!

August 17th, 2015
Another Fermat factor from FermatSearch!
1127899657 . 2^{3732}+1 is a Factor of
F_{3730}!!!
Takahiro Nohara found his 13th Fermat factor today, the fourth factor of this year.
Congratulations from Fermatserch!

August 13th, 2015
New Fermat factor from FermatSearch!
787703529 . 2^{3854}+1 is a Factor of
F_{3850}!!!
Maximilian Pacher found his 6th Fermat factor using NewPGen, PRP and WinPFGW for his test.
Congratulations to Maxi from FermatSearch, for the third factor of the year!

July 21st, 2015
New Fermat factor from FermatSearch!
1132007355 . 2^{3578}+1 is a Factor of
F_{3576}!!!
Takahiro Nohara found a new Fermat factor using an i7 Ivybridge processor with 4GB of RAM, sieving by Fougeron's FermFact, and found as a prime using PFGW.
Congratulations to Takahiro Nohara from FermatSearch, for his 12th factor, the second of the year!

February 13th, 2015
A new factor from PrimeGrid!
267 . 2^{2662090}+1 is a Factor of
F_{2662088}!!!
Congratulations Jay Parangalan from the PrimeGrid group, we begin this year with a new Fermat factor!

December 27th, 2014
A new factor after only one week!
465917283 . 2^{4189}+1 is a Factor of
F_{4184}!!!
Serge Batalov found his sixth Fermat factor! Sieved by Fougeron's FermFact, found as a prime using PFGW.
Congratulations to Serge, we close this year with 7 new Fermat factors!

Deceber 20th, 2014
New Fermat factor from FermatSearch!
44670651 . 2^{9749}+1 is a Factor of
F_{9747}!!!
Takahiro Nohara found a new Fermat factor using an i7 Ivybridge processor with 4GB of RAM, sieving by Fougeron's FermFact, and found as a prime using PFGW.
Congratulations to Takahiro Nohara from FermatSearch, for the sixth factor of the year!

October 22nd, 2014
New Fermat factor from FermatSearch!
79425 . 2^{100520}+1 is a Factor of
F_{100518}!!!
Payam Samidoost found his fifth Fermat factor! Sieved by Fougeron's FermFact, found as a prime using Penné's LLR and revealed as a Fermat factor by Fougeron's PFGW.
Congratulations to Payam Samidoost from FermatSearch, for the fifth factor of the year!

July 25th, 2014
PrimeGrid strikes again!
193 . 2^{3329782}+1 is a Factor of
F_{3329780}!!!
Raymond Ottusch found the
largest Fermat Divisor ever discovered! He used PSieve, SrSieve and LLR for this discovery.
Congratulations to Raymond and the staff of PrimeGrid for their giant factor!

June 26th, 2014
mmff discovers a new Fermat prime!
48595346636925 . 2^{197}+1 is a Factor of
F_{195}!!!
Serge Batalov found his fifth Fermat factor using a version of mmff extended by himself, for this discovery.
Congratulations to Serge from FermatSearch, for the third factor of the year!

June 22th, 2014
mmff0.28 is out!
The next set of 32 N values in k*2
^{N}+1 Fermat factor testing is available.
The highest testable N is now 223, and the highest bitlevel is 252.
Practically, the highest usable N is 207 (was 175 is version 0.27).
As always, previous savefiles will not work with 0.28 unless the nocheck argument is used.
A big thank you to Serge Batalov who updated the code!

May 26th, 2014
The Number of the Beast is not prime!
217924552867 . 2^{668}+1 is a Factor of
F_{666}!!!
Roman Maznichenko found his fifth Fermat factor using an Intel (Haswell) i54670K@4000GHz and Feromant, a program he wrote, for this discovery.
Congratulations to Roman from FermatSearch, for the second factor of the year!

March 14th, 2014
New Fermat factor from FermatSearch!
209161375 . 2^{4262}+1 is a Factor of
F_{4260}!!!
Takahiro Nohara found his tenth Fermat factor using NewPGen 2.82 for sieve, PFGW 3.7.5 for PRP and GFN divisibility testing for this discovery.
Congratulations to Takahiro Nohara from FermatSearch, for the first factor of the year!

August 16th, 2013
Another Fermat factor from PrimeGrid!
2145 . 2^{1099064}+1 is a Factor of
F_{1099061}!!!
PrimeGrid user Say Yik Tang & PrimeGrid found another giant Fermat factor.
They used PSieve, SrSieve and LLR program for this discovery.
The factor was submitted to Chris Caldwell's database on June 21th, 2013, and modified only on August 16th.
Congratulations to user Say Yik Tang and PrimeGrid for the 7th factor of the year!

June 23rd, 2013
Another Fermat factor from PrimeGrid!
183 . 2^{1747660}+1 is a Factor of
F_{1747656}!!!
Bart van Rooijen & PrimeGrid found another giant Fermat factor.
They used PSieve, SrSieve and LLR program for this discovery.
The factor was submitted to Chris Caldwell's database on March 10th, 2013, but it was published only on June 23rd.
Congratulations to Bart and PrimeGrid for the 6th factor of the year!

May 14th, 2013
New Fermat factor from PrimeGrid!
57 . 2^{2747499}+1 is a Factor of
F_{2747497}!!!
Marshall Bishop & PrimeGrid found this giant Fermat factor less than a week after Ryan Propper.
He used LLR program for his discovery.
Congratulations to Marshall and PrimeGrid for the 5th factor of the year!

May 8th, 2013
Ryan Propper found a new factor!
5449229488169 . 2^{465}+1 is a Factor of
F_{459}!!!
Less than 4 months after the last discoveries, Ryan Propper broke the dry spell and found his first factor a few weeks after joining FermatSearch.
He used "a 100 core Linux cluster" and GMPFermat by Mark Rodenkirch for his discovery.
Congratulations from the team of FermatSearch for the 4th factor of the year!

March 25th, 2013
PFGW 3.7.5 released
Mark Rodenkirch released a newer version of PFGW for Linux, MAC and Windows.
This new release corrects a bug on the GFN and xGF factoring.
Please visit the downlod page and update your older version now.

February 14th, 2013
PFGW 3.7.3 released
Mark Rodenkirch released a newer version of PFGW for Linux, MAC and Windows.
This new release has all the innovations of the last GWNUM library, and corrects some bugs on the Win 32bit version.
Please visit the downlod page and update your older version now.

January 30th, 2013
Roman Maznichenko strikes again!
303472680883 . 2^{420}+1 is a Factor of
F_{417}!!!
After the "fourfactorsinarow" from Serge Batalov, Roman Maznichenko found 2 new factors in less than 24 hours.
This time he used an AMD FX8350 @4000MHz and GMPFermat by Mark Rodenkirch for his test.
Congratulations from the team of FermatSearch for his 4th factor, the 3rd of the year! (Now we all ask for more...)

January 29th, 2013
Roman Maznichenko found his 3rd factor!
1210895760431083 . 2^{68}+1 is a Factor of
F_{65}!!!
Maxi found the factor using mmff and his Nvidia GTX 580, it the 2nd factor of this year.
He reached his goal after 5 months of continuous search.
Congratulations Roman!

January 18th, 2013
Maximilian Pacher found his 5th factor!
406860969 . 2^{3322}+1 is a Factor of
F_{3314}!!!
Maxi found the 309th factor of a Fermat number, the 1st factor of this year.
He used NewPGen, PRP and WinPFGW for his test.
Congratulations from the team of FermatSearch!

December 27th, 2012
Serge Batalov found his 4th factor this year!
10111717305 . 2^{1136}+1 is a Factor of
F_{1132}!!!
Serge Batalov found the 308th factor of a Fermat number. and the 16th this year.
He used GMPFermat.exe by Mark Rodenkirch for his testing of the range 1000 ≤ N ≤ 1199, 6,000,000,000 ≤ k ≤ 20,000,000,000.
Congratulations from the team of FermatSearch!

December 13th, 2012
New release of mmff!
George Woltman released
mmff v0.27, a program written to test Fermat and Double Mersenne numbers using the power of
GPU: it can now test numbers between F
_{26} and F
_{174}!!!
Go and check it on the
download page!

December 7th, 2012
Another Fermat factor found!!!
2864929972774011 . 2^{41}+1 is a Factor of
F_{39}!!!
Tapio Rajala of Finland found his third Fermat factor, the 307th factor discovered.
Tapio found the factor using the new
mmff.exe program written by
George Woltman, optimized for nvidia GPUs.
It is the first factor discovered with mmff.exe!
Congratulations, Tapio!

November 21st, 2012
Serge strikes again! Found a third new Fermat factor after only 8 days!!!
3860269 . 2^{17750}+1 is a Factor of
F_{17748}!!!
Serge Batalov found his third Fermat factor, the 306th factor discovered.
Serge had access to a big computer farm, and with big effort and a little luck discovered another gem.
This year has been the richest in factors found since the release of Leonid Durman's 'Factor.exe, 2001, and the start of FermatSearch project.
Serge, leave some factors to us!

November 13th, 2012
New Fermat factor after only 4 days!
30967 . 2^{106436}+1 is a Factor of
F_{106432}!!!
Serge Batalov found another big factor, his second, and the 305th factor discovered.
Serge Batalov used NewPGen.exe by Paul Jobling for sieving and
pfgw.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!

November 9th, 2012
Found a new Fermat factor!
5505161 . 2^{9449}+1 is a Factor of
F_{9447}!!!
The factor was discovered by Serge Batalov of USA, it is his first Fermat factor, and the 304th factor discovered.
Serge Batalov used NewPGen.exe by Paul Jobling for sieving and
pfgw.exe for PRP test and xGFN divisibility test.
Congratulations Serge!

October 27th, 2012
Vacation!!!
After more than 14 month of hard work, I will finally enjoy a pause from Nov. 2nd to Nov. 26th..
If you are close to finishing a range, or just need to reserve some more work for next month, please do it
now.
Reservations and results will be gathered as usual on a firstcome, first served base. Ranges come after Nov. 1st won't get lost, but will be delayed until I come back home to assign them.

October 10th, 2012
Found a new Fermat factor!
143918649 . 2^{4654}+1 is a Factor of
F_{4652}!!!
The factor was discovered by Tapio Rajala of Finland, it is his second Fermat factor, and the 303rd factor discovered.
Tapio Rajala used NewPGen.exe by Paul Jobling for sieving and
pfgw.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!

October 1st, 2012
New fast program to test Fermat numbers!
George Woltman, head of GIMPS and programmer of Prime95, the fastest code to test Mersenne numbers, developed and released
mmff, a program written to test Fermat and Double Mersenne numbers using the power of
GPU: it is more than 50 times faster than any other program for numbers between F
_{26} and F
_{145}!!!
Go and check it on the
download page!

August 3rd, 2012
New Fermat factor found!
72179955 . 2^{4269}+1 is a Factor of
F_{4265}!!!.
The factor was discovered by Takahiro Nohara of Japan, it is his ninth Fermat factor, and the 302nd factor discovered.
Takahiro Nohara used NewPGen.exe by Paul Jobling for sieving and
OpenPFGW.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!

July 10th, 2012
New Fermat factor after 3 days!
2674670937447 . 2^{171}+1 is a Factor of
F_{166}!!!.
The factor was discovered by Roman Maznichenko from Russia using a AMD FX8120 @3800MHz and his version of Mark Rodenkirch's GMPFermat. This is the fourth factor found by GMPFermat, and the second found by Roman Maznichenko.
We have discovered 9 factors in less than 7 months, the same total of the whole 2011, and we keep going!
Congratulation from FermatSearch, Roman!

July 7th, 2012
300th Fermat factor found!
20018578522347 . 2^{88}+1 is a Factor of
F_{86}!!!.
The factor was discovered by Michael Dangler of USA, using Mark Rodenkirch's program GMPFermat, and is the eighth factor discovered this year.
The factor was found using this environment:
 Windows 7 Home Premium 64bit Operating System
 Toshiba Satellite P775
 Intel(R)Core(TM)i72670QM CPU @2.20GHZ 6.00 GB Memory
Michael found the factor on its eleventh testrange, after only a few months of testing.
Congratulations from the team of FermatSearch!

June 17th, 2012
New Fermat factor found!
262254673 . 2^{3706}+1 is a Factor of
F_{3703}!!!.
The factor was discovered by Takahiro Nohara of Japan, it is his eighth Fermat factor, and the seventh factor discovered this year.
Takahiro Nohara used NewPGen.exe by Paul Jobling for sieving and
OpenPFGW.exe for PRP test and xGFN divisibility test.
Congratulations from the team of FermatSearch!

June 13th, 2012
Sixth Fermat factor of 2012!
On June 13th, 2012, and as part of PrimeGrid's Proth Prime Search, Robert Boniecki found the following new factor of a Fermat number:
1705 . 2^{906110}+1 is a Factor of
F_{906108}!!!.
The number has 272770 digits and is the 298th Fermat factor discovered. Will we be able to reach 300 factors by the end of the year?
The credits for the discovery are as follows:
1. Robert Boniecki, discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
5. LLR, primality program developed by Jean Penné
6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Robert and to the leading organizers of PrimeGrid!

May 31st, 2012
Fifth Fermat factor of 2012!
On May 31, 2012, and as part of PrimeGrid's Proth Prime Search, James Boerner found the following new factor of a Fermat number:
7905 . 2^{352281}+1 is a Factor of
F_{352279}!!!.
The credits for the discovery are as follows:
1. James Boerner, discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
5. LLR, primality program developed by Jean Penné
6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to James and to the leading organizers of PrimeGrid!

March 28, 2012
FermatSearch strikes again!
4785972759 . 2^{954}+1 is a Factor of
F_{943}!!!.
The factor was discovered by Andriy Sen of Ukraine, and is the fourth factor of this year.
He used GMPFermat.exe on a Windows Server 2008 R2 Standard x64, Intel Core2 CPU 6600 @ 2.40 GHz to test it.
Andriy found his factor while testing N=900989 and k=4,000,000,0005,000,000,000.
Congratulations from the team of FermatSearch!

March 11, 2012
Seventh Fermat factor found by Takahiro Nohara!
238451805 . 2^{2608}+1 is a Factor of
F_{2606}!!!.
The factor was discovered by Takahiro Nohara of Japan, and is the third factor of this year.
He used NewPGen.exe by Paul Jobling for sieving and
OpenPFGW.exe for PRP test and xGFN divisibility test.
Takahiro found his factor while testing N=20052999 and k=60,000,000400,000,000 exactly on the first anniversary of the earthquake and tsunami disaster
that triggered also a nuclear accident in Fukushima.
Congratulations from the team of FermatSearch!

February 7th, 2012
Second Fermat factor of 2012!
On 4 Jan 2012 0:34:57 UTC, PrimeGrid's Proth Prime Search project found a prime Fermat
divisor:
131 . 2^{1494099}+1 is a Factor of
F_{1494096}!!!.
The prime is 449,771 digits long and will enter Chris Caldwell's "The Largest Known Primes
Database" ranked 6th for prime Fermat divisors and 292nd overall. It is the 2nd divisor found in 2012 and 294th overall.
The discovery was made by Rob Derrera of the United States using an Intel Core i7 960 @
3.20GHz with 24 GB RAM running Windows 7 Ultimate x64. This computer took just over 53
minutes to complete the primality test using LLR. Rob is a member of the US Navy team.
The prime was verified on 7 Feb 2012, 4:56:41 UTC, by Sergey Iovov of the Ukraine using an
Intel Xeon X5650 @ 2.67GHz with 24 GB RAM running Windows Server 2008 Standard x64.
This computer took 53 minutes 45 seconds to complete the primality test using LLR.
The credits for the discovery are as follows:
1. Rob Derrera (United States), discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
5. LLR, primality program developed by Jean Penné
6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Rob and to the leading organizers of PrimeGrid!

January 6th, 2012
First Fermat factor of 2012!
On 4 Jan 2012 0:34:57 UTC, PrimeGrid's Proth Prime Search project found a prime Fermat
divisor:
329 . 2^{1246017}+1 is a Factor of
F_{1246013}!!!.
The prime is 375,092 digits long and will enter Chris Caldwell's "The Largest Known Primes
Database" ranked 6th for prime Fermat divisors and 522nd overall. It is the 1th divisor found in 2012 and 293rd overall.
The discovery was made by Bruce Dodson of the United States using an Intel Xeon MP @
2.80GHz with 12 GB RAM running Linux. This computer took just over 3 hours and 25 minutes
and 28 seconds to complete the primality test using LLR. Grzegorz is a member of the Sicituradastra Team.
The prime was verified on 6 January 2012 17:41:07 UTC, by Ovidiu Cioca of Canada using
an Intel Core2 6700 @ 2.66GHz with 4 GB RAM running Windows XP. This computer took 29 minutes and 45 seconds to complete the primality test using LLR.
The credits for the discovery are as follows:
1. Bruce Dodson (United States), discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
5. LLR, primality program developed by Jean Penné
6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Bruce and to the leading organizers of PrimeGrid!

September 9, 2011
Nine Fermat factors found in 9 months! Will we be able to reach 12 this year?
On 9 Sep 2011 11:50:50 UTC, PrimeGrid's Proth Prime Search project found a prime Fermat
divisor:
25 . 2^{2141884}+1 is a Factor of
F_{2141872}!!!.
The prime is 644,773 digits long and will enter Chris Caldwell's "The Largest Known Primes
Database" ranked 5th for prime Fermat divisors and 88th overall. It is the 9th divisor found in 2011 and 292nd overall.
The discovery was made by Grzegorz Granowski of Poland using an Intel Xeon X5550 @
2.67GHz with 12 GB RAM running Windows Vista x64. This computer took just over 58 minutes
and 28 seconds to complete the primality test using LLR. Grzegorz is a member of the Polish
National Team.
The prime was verified on 11 Sep 2011 12:02:18 UTC, by John R. H. Graham of Canada using
an Intel i7 920 @ 2.67GHz with 12 GB RAM running Windows 7 x64. This computer took about 1
hour and 47 minutes to complete the primality test using LLR. John is a member of Team
Canada.
The credits for the discovery are as follows:
1. Grzegorz Granowski (Poland), discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
5. LLR, primality program developed by Jean Penné
6. OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Grzegorz and to the leading organizers of PrimeGrid!

September 1, 2011
News from the
download page!
New PFGW for Windows, MAC and Linux, and fermfact 2.0 added today.

July 8, 2011
Another Fermat factor from PrimeGrid!
On 8th July 2011 02:22:20 UTC, PrimeGrid's Proth Prime Search project, through PRPNet, found a prime Fermat divisor:
4479 . 2^{226618}+1 is a Factor of
F_{226614}!!!.
The prime is 68,223 digits long. It is the 8th divisor found in 2011 and 291th overall.
The discovery was made by Peter Doggart of the United Kingdom using an AMD Phenom 9600 X4 @ 2.3 GHz with 3 GB RAM running 32 bit Windows 7. This computer took 78 seconds to complete the primality test using LLR.
The credits for the discovery are as follows:
1. Peter Doggart (United Kingdom), discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
5. LLR, primality program developed by Jean Penné
6. OpenPFGW, a primality program developed by Chris Nash and Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Peter and to the leading organizers of PrimeGrid!

July 5, 2011
Seven Fermat factors found in 7 months!
43714055 . 2^{3337}+1 is a Factor of
F_{3335}!!!.
The factor was discovered by Nikolay Kamenyuk of Ukraine, and is the seventh factor of this year. We now have 250 Fermat numbers known to be composite,
and "10 to go" to reach 300 prime factors overall.
Nikolay found his factor while testing N=30014000 and k=40,000,000100,000,000.
Congratulations Nikolay!

July 1, 2011
PrimeGrid strikes again!
On 1 July 2011 02:59:41 UTC, PrimeGrid's Proth Prime Search project, through PRPNet, found a prime Fermat divisor:
3771 . 2^{221676}+1 is a Factor of
F_{226170}!!!.
The prime is 66,736 digits long. It is the 6th divisor found in 2011 and 289th overall.
The discovery was made by Mark Doom of the United States using an AMD Phenom II X6 1090T with 2 GB RAM running Windows 7 x64. This computer took 40 seconds to complete the primality test using LLR.
The credits for the discovery are as follows:
1. Mark Doom (United States), discoverer
2. PrimeGrid, et al.
3. Srsieve, sieving program developed by Geoff Reynolds
4. PSieve, sieving program developed by Ken Brazier and Geoff Reynolds
5. LLR, primality program developed by Jean Penné
6. OpenPFGW, a primality program developed by Chris Nash and Jim Fougeron with maintenance and improvements by Mark Rodenkirch
Congratulations go to Mark and to the leading organizers of PrimeGrid!

June 23, 2011
New Fermat factor discovered after 1 day!
7333 . 2^{138560}+1 is a Factor of
F_{138557}!!!.
The factor was discovered by Dirk D'huyvetters of Belgium coadiuvated by the PrimeGrid team. This is the 288th known divisor fifth factor found this year.
This factor was the first of the three disconvered in March, but only during the recent doublechecking for GFN divisibilities the factor was revealed, as the team was focused on Proth Primes and not Fermat factors.
Congratulations go to Dirk and to the leading organizers of PrimeGrid: John Blazek, Rytis Slatkevičius and Lennart Vogel!

June 22, 2011
New recordsize Fermat factor!
As part of PrimeGrid's Proth Prime Search, Scott Brown (USA) found the following new factor of a Fermat number:
9 . 2^{2543551}+1 is a Factor of
F_{2543548}!!!.
This factor 765,687 digits long exceeds in size the prime factor
3 . 2^{2478785}+1 of
F_{2478782} discovered on October 10, 2003 and therefore
is currently the largest known divisor of a Fermat number!
Congratulations to everyone involved in this remarkable discovery!!

March 20, 2011
New Fermat factor after 5 days!
111318179143061 . 2^{45}+1 is a Factor of
F_{42}!!!.
The factor was discovered by Roman Maznichenko from Russia using Mark Rodenkirch's GMPFermat. This is the first factor found by GMPFermat.
Roman worked hard on ECM also, and we all hope he will find another factor soon.
Congratulation, Roman!

March 15, 2011
Second Fermat factor of 2011!
14783975791554494074552473179612897725474511 . 2^{19}+1 is a Factor of
F_{17}!!!.
The factor was discovered by David Bessell from St Michael's Collegiate School in Australia using Prime95. This is the third factor found by David while computing ECM curves on small Fermat numbers.
The cofactor of F17 has around 39,000 digits, and has been proven composite.
Congratulation, David!

February 21, 2011
FermatSearch.org has a
new server ! To guarantee better performances to our users, your webmaster has taken the opportunity to upgrade the old hardware and install a new more powerful one. Please let me know about every possible glitch that may have occurred during the migration of data.

February 5, 2011
GMPFermat 2.1 for Windows 64 bit version has passed its checks!!!.
Thanks to Matt Anderson (who addressed the issue on MersenneForum) and Brian Gladman (who offered his programming skills), we now finally have a GMPFermat version with superfast assembly routines written by Geoff Reynolds and running on Windows 64bit platforms!
The new executable can be found on the
Download page.
Wonderful job, Brian and Matt, thank you!

January 12, 2011
First Fermat factor of 2011!
837747239 . 2^{1203}+1 is a Factor of
F_{1201}!!!.
The factor was discovered by our old friend Maximilian Pacher, from Austria, using NewPGen, PRP and PFGW programs. Maxi could have found this factor seven years ago if his range were not limited to 1200.
This is his fourth Fermat factor"
Congratulation, Maxi!

December 9, 2010
GMPFermat 2.1 for Windows 64 bit version is out!!!.
Thanks to Matt Anderson (who addressed the issue on a forum) and Brian Gladman (who offered his programming skills), we now finally have a GMPFermat version with superfast assembly routines written by Geoff Reynolds and running on Windows 64bit platforms!
The new executable can be found on the
Download page.
Wonderful job, Brian and Matt, thank you!

November 20, 2010
A second new Fermat factor has been found on November 20!
272392805475 . 2^{304}+1 is a Factor of
F_{299}!!!.
The factor was discovered by Alexey Komkov, from Russia, using his own program written in Borland C++ builder. Alexey has been testing a huge range using 30 P4 computers in the last 6 months.
Congratulation, Alexey!

November 8, 2010
A totally new Fermat factor has been found!
103257279 . 2^{2422}+1 is a Factor of
F_{2420}!!!.
The factor was discovered by Peter Strasser, from Austria, on November 7th, 2010. Peter was testing a huge range with his own program based on Mathematica.
Congratulation, Peter!

March 27, 2010
Five in a row! Michael Vang (USA) found a new Fermat factor:
17353230210429594579133099699123162989482444520899 . 2^{15}+1 is a Factor of
F_{12}!!!.
Mike found this factor after 5200 curves ran on F12.
Software used: GMPECM 6.2. The cofactor is still composite.
He used two AMD Phenom X4 9550 quad core boxes with 6GiB RAM each, running on Debian Linux.
Congratulations Mike!

March 26 2010
Third Fermat factor from GIMPS! David Bessel found a new Fermat factor:
3853959202444067657533632211 . 2^{24}+1 is a Factor of
F_{22}!!!.
The factor has been discovered by David Bessell from St Michael's Collegiate School in Australia using Prime95, while testing some ECM curves on F22.
It is the seconf Fermat factor discovered by David Bessell in less than one year, after more than 15,500 GHzDays.
The cofactor is still composite...
Congratulations to Mr. David Bessell!

March 26, 2010
PFGW 3.3.3 for Windows, Linux and MAC is out!!!.
Mark Rodenkirch released another, faster, version of PFGW for Windows, Linux and MAC, based on v25.14 of gwnum library.
The major change in this release is that it has been updated to use gwnum 25.14, which addresses the following issues:
* Gwnum would lose the /d in some (k*b^n+c)/d cases. This happened primarily in cases where the number was between 300 and 350 bits.
* The final conversion from gwnum to binary could fail in cases where generic reduction was used. The larger the number the less likely the bug would occur.
* Zero padded FFTs of length 80 and 112 could fail.
* More conservative in selecting an FFT length for nonbase2 cases.
This release also goes back to using rational FFTs, which are slightly faster than irrational FFTs.
With these changes to gwnum, there will be fewer roundoff errors with PFGW. These changes also address primality tests that silently fail. "Silently fail" refers to tests that do not trigger roundoff errors, yet have an incorrect result. It is highly recommended to update your clients to this release.
The new executable can be found on the
Download page.
Wonderful job, Mark, thank you!

March 15, 2010
Another factor comes from FermatSearch! Cedric Vonck found a new Fermat factor:
81909357657279 . 2^{54}+1 is a Factor of
F_{52}!!!.
Cedric found this factor while testing his first range, how lucky!
Software used: Fermat.exe
The new factor is the third Fermat factor discovered in 2010.
Congratulations to Mr. Cedric Vonck!

February 3, 2010
GIMPS strikes again! Tapio Rajala (Department of Mathematics and Statistics  University of Jyväskylä, Finland) found a new Fermat factor:
1784180997819127957596374417642156545110881094717 . 2^{16}+1 is a Factor of
F_{14}!!!.
Tapio found this factor after approximately 750 curves ran on F14 with B1=110M.
Software used: Prime95
Note that F14 was the first Fermat number without known factors. The cofactor, C4880, is composite.
The new factor is the second Fermat factor discovered in 2010, and the second discovered by GIMPS using Elliptic Curves Method.
Congratulations to Mr. Tapio Rajala!

January 25, 2010
Sergei Maiorov found a new Fermat factor:
84977118993 . 2^{520}+1 is a Factor of
F_{517}!!!.
"It's my first Fermat factor, and also the first one of 2010!"
Software used: Fermat.exe 4.4
Congratulations to Mr. Sergei Maiorov!

January 11, 2010
PFGW 3.3.0 for Linux and MAC, and
3.3.1 for WIndows are out!!!.
Mark Rodenkirch released another, faster, version of PFGW for Windows, Linux and MAC, based on v25.13 of gwnum library.
The new executable can be found on the
Download page.
Wonderful job, Mark, thank you!

Compiled by Luigi Morelli