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 2013-04-03, 00:53 #1 Jeff Gilchrist     Jun 2003 Ottawa, Canada 3·17·23 Posts Big factors Found my biggest factor so far for a Wagstaff number: 2^9235649+1 has a factor: 153616228560877782360733142221974579132477827835600631264993134521609 [226.5 bits]
 2013-04-03, 01:23 #2 Batalov     "Serge" Mar 2008 Phi(4,2^7658614+1)/2 19·232 Posts worktodo.txt: Pminus1=1,2,8232929,1,10000,0,"3" => Code: P-1 found a factor in stage #1, B1=10000. 2^8232929+1 has a factor: 997183410304432117267065463213026379715216410911450070172292068758243 [That's 229.2 bits] (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.)
 2013-04-03, 01:24 #3 dleclair     Mar 2003 10011112 Posts Congratulations, Jeff!
 2013-04-03, 02:05 #4 ixfd64 Bemusing Prompter     "Danny" Dec 2002 California 1001101111012 Posts Have you submitted them to Zimmermann's website? http://www.loria.fr/~zimmerma/records/Pminus1.html
 2013-04-03, 02:20 #5 Batalov     "Serge" Mar 2008 Phi(4,2^7658614+1)/2 19×232 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: P-1 found a factor in stage #1, B1=100000. 2^8232929+1 has a factor: 8203927240046868961280630569987984778892578839825012457683394506843242760078451651993971 [292 bits]
 2013-04-03, 02:23 #6 paulunderwood     Sep 2002 Database er0rr 2·33·83 Posts Vincent TF'd Jeff's Wagstaff candidate to 61 bits Last fiddled with by paulunderwood on 2013-04-03 at 02:29
 2013-04-03, 02:44 #7 ixfd64 Bemusing Prompter     "Danny" Dec 2002 California 32·277 Posts Damn. But it's pretty cool to find a factor that divides into three other ones.
2013-04-03, 19:05   #8
Batalov

"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

1005110 Posts

Quote:
 Originally Posted by paulunderwood Vincent TF'd Jeff's Wagstaff candidate to 61 bits
Isn't it fairly obvious to use a slightly revised mfaktc for that?

This is how far you guys TF? 61 bits? This is very low.

2013-04-03, 19:23   #9
TimSorbet
Account Deleted

"Tim Sorbera"
Aug 2006
San Antonio, TX USA

10B716 Posts

Quote:
 Originally Posted by Batalov Isn't it fairly obvious to use a slightly revised mfaktc for that? This is how far you guys TF? 61 bits? This is very low.
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"?)

 2013-04-03, 19:37 #10 paulunderwood     Sep 2002 Database er0rr 106028 Posts Oliver has modified his GPU code and Jeff is testing it now. Vincent should be firing up a couple of Teslas soon.
 2013-04-07, 11:07 #11 Jeff Gilchrist     Jun 2003 Ottawa, Canada 49516 Posts As Paul said, we are factoring to high bits now with the modified version of mfaktc. That P-1 factor was from the last batch of p-1 before I started using it. GPU TF FTW!

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