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#1 |
May 2003
60B16 Posts |
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I just found my first decent sized factor using ECM. It's a 44 digit probable prime factor coming from 16651^13-1. (It's one of the composites on the OPN website.)
Just wanted to share my joy. :) |
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#2 | |
Nov 2003
11101001001002 Posts |
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Huh???? ![]() ![]() ![]() (16651^13 -1)/16650 is itself only 51 digits...... It is divisible by 30187, leaving a composite of only 47 digits... Perhaps you wrote the wrong number? |
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#3 |
"Phil"
Sep 2002
Tracktown, U.S.A.
3·373 Posts |
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The exponent should have been written 31, not 13. The composite factor he was working on is listed at www.oddperfect.org as having 110 digits.
Congratulations! |
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#4 |
May 2003
7·13·17 Posts |
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R. D. Silverman,
Woops! Yeah, Philmoore got it. 31 is right. :) (Oh, and I hope there are no bad feelings about the religion thread.) Best, Pace Last fiddled with by Zeta-Flux on 2005-05-10 at 16:51 |
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#5 | |
Mar 2003
New Zealand
13·89 Posts |
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#6 | |
"William"
May 2003
New Haven
2,371 Posts |
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The SNFS difficulty was 131 digits. The rule of thumb is ECM for 2/9 the size then SNFS. So SNFS would probably have been a better choice than ECM once the 30 digit level was passed. |
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#7 |
May 2003
7×13×17 Posts |
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wblipp,
First, thanks for your comments. Know that if there was an easy way to do SNFS I would probably take a crack at it. From what I've read on this forum, to do SNFS takes quite a bit of effort. Unlike ECM, you can't just plug in the number into a program and let it run. I'm smart enough to probably figure it out one day, but for now I'm just having fun with ECM. :) Second, know that there are an quite a few other unclaimed composite numbers on the site that SNFS people can have fun with, and I just felt like giving ECM a try for a while. Fortunately, I found a factor after only a few days. So, by sheer luck, I didn't have to watch the number of tried curves mount up. geoff, Thanks! Fortunately (and surprisingly) it only took a few curves! |
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#8 | |
"Nancy"
Aug 2002
Alexandria
46438 Posts |
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Alex |
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#9 | |
"William"
May 2003
New Haven
2,371 Posts |
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I also want to urge people towards the most efficient methods. I haven't figured out how to do that without coming across as a churlish ungrateful troll. Maybe when the work situation calms down a bit I can put together some web pages of guidelines for which method and how to set it up. For now, thanks for the factors and I'm glad you are having fun. |
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#10 |
May 2003
7×13×17 Posts |
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I didn't realize that some of the numbers were better suited to ECM. Wblipp, go ahead and de-reserve the C112 for me, and instead I'll work on the C135 (which looks to be the least fitted to SNFS).
Hope that cheers everyone up! :D |
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#11 |
"Nancy"
Aug 2002
Alexandria
2,467 Posts |
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Yep, at difficulty 200, 547^73-1 c135 is a worthwhile target for ECM. By the 2/9 rule of thumb, ECM to 45 digits would suffice to justify switching to SNFS, but as NFS sievers are in notoriously short supply, going a little further and running a couple of curves at B1=44M as well wouldn't hurt...
Good luck! Alex |
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