20130403, 00:53  #1 
Jun 2003
Ottawa, Canada
10010010001_{2} Posts 
Big factors
Found my biggest factor so far for a Wagstaff number:
2^9235649+1 has a factor: 153616228560877782360733142221974579132477827835600631264993134521609 [226.5 bits] 
20130403, 01:23  #2 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2·7·11·59 Posts 
worktodo.txt:
Pminus1=1,2,8232929,1,10000,0,"3" => Code:
P1 found a factor in stage #1, B1=10000. 2^8232929+1 has a factor: 997183410304432117267065463213026379715216410911450070172292068758243 (Of course, I cheated in Pari first, by finding a few 2^p+1 that have at least five small factors. This one has two more slightly larger. Seven altogether.) 
20130403, 01:24  #3 
Mar 2003
3×5^{2} Posts 
Congratulations, Jeff!

20130403, 02:05  #4 
Bemusing Prompter
"Danny"
Dec 2002
California
2292_{10} Posts 
Have you submitted them to Zimmermann's website?
http://www.loria.fr/~zimmerma/records/Pminus1.html 
20130403, 02:20  #5 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2×7×11×59 Posts 
Composite factors are not eligible:
153616228560877782360733142221974579132477827835600631264993134521609 = 7160401272398244691 * 219902328863708115073 * 97559577016295905770143558963 The smallest of them should have been found by TF, easily: 62 bits. (Wagstaff numbers have factors of form 2kp+1, just like Mersenne's.) Let's find some even larger factors... Code:
P1 found a factor in stage #1, B1=100000. 2^8232929+1 has a factor: 8203927240046868961280630569987984778892578839825012457683394506843242760078451651993971 
20130403, 02:23  #6 
Sep 2002
Database er0rr
110100001011_{2} Posts 
Vincent TF'd Jeff's Wagstaff candidate to 61 bits
Last fiddled with by paulunderwood on 20130403 at 02:29 
20130403, 02:44  #7 
Bemusing Prompter
"Danny"
Dec 2002
California
4364_{8} Posts 
Damn. But it's pretty cool to find a factor that divides into three other ones.

20130403, 19:05  #8 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2×7×11×59 Posts 

20130403, 19:23  #9 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
17×251 Posts 
Don't forget that TF to 61 bits for a number with p=9M is much harder than TF to 61 with p=64M. I think it's more like TFing p=64M to 64 bits...that still seems low, but for p=9M, maybe that's sufficient. Maybe they don't have an mfaktc equivalent. ("wfaktc"?)

20130403, 19:37  #10 
Sep 2002
Database er0rr
3^{2}·7·53 Posts 
Oliver has modified his GPU code and Jeff is testing it now. Vincent should be firing up a couple of Teslas soon.

20130407, 11:07  #11 
Jun 2003
Ottawa, Canada
7×167 Posts 
As Paul said, we are factoring to high bits now with the modified version of mfaktc. That P1 factor was from the last batch of p1 before I started using it.
GPU TF FTW! 
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