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2017-06-09, 17:34   #309
paulunderwood

Sep 2002
Database er0rr

2·3·19·31 Posts

Quote:
 Originally Posted by alpertron The 315th in the list is: M611999 = 18464214225958267477777390354183 * PRP184199
FWIW

Code:
time ../../coding/gwnum/lucasPRP M611999-cofactor 1 2 611999 -1
Lucas testing on x^2 - 9*x + 1 ...
Is Lucas PRP!

real	2m21.692s
user	5m2.932s
sys	2m41.120s

 2017-09-03, 11:14 #310 axn     Jun 2003 2·52·97 Posts Sometime during Aug 31/Sep 1, a P68 was reported for M1471, completing its factorization, making it #316 EDIT:- The cofactor is a proven prime, so mersenne.ca status can be changed from PRP to P Last fiddled with by axn on 2017-09-03 at 11:18
2017-09-03, 13:16   #311
GP2

Sep 2003

32·7·41 Posts

Quote:
 Originally Posted by axn Sometime during Aug 31/Sep 1, a P68 was reported for M1471, completing its factorization, making it #316 EDIT:- The cofactor is a proven prime, so mersenne.ca status can be changed from PRP to P
OK, it now shows as a proven prime at mersenne.ca, based on the certificate at factordb.com

The new factor showed up at FactorDB and at mersenne.ca, but not at mersenne.org... presumably mersenne.ca and mersenne.org exchange data both ways daily, so it would get there eventually? But I decided to manually report it to mersenne.org anyway, just to be sure...

"Insufficient information for accurate CPU credit. For stats purposes, assuming factor was found using ECM with B1 = 50000. CPU credit is 0.0000 GHz-days."

If the actual discoverer is a GIMPS user, maybe the database can be adjusted.

2017-09-11, 18:08   #312
GP2

Sep 2003

258310 Posts

Quote:
 Originally Posted by axn Sometime during Aug 31/Sep 1, a P68 was reported for M1471, completing its factorization, making it #316 EDIT:- The cofactor is a proven prime, so mersenne.ca status can be changed from PRP to P
It occurred to me to run a screenscraping script to collect all Mersenne exponents under 10,000 known to FactorDB, and crosscheck them with the GIMPS database. I found one more new factor there:

M1489 has a factor: 95909518295775374166321292697000685895150503357477127

(53 digits)

It was reported (by who?) to FactorDB on August 17. The remaining 295-digit cofactor is composite, however.

Does anyone know who this person is, who is finding large new factors for very small Mersenne exponents, independently of GIMPS.

Just a month ago, I ran a systematic crosscheck of exponents under 1 million (prompted by this thread), and synchronized the data on both FactorDB and GIMPS. Obviously it will be worthwhile to keep checking FactorDB every few weeks, for the very small exponents at least, to see if new ones keep cropping up.

Last fiddled with by GP2 on 2017-09-11 at 18:11

2017-09-11, 18:54   #313
xilman
Bamboozled!

"𒉺𒌌𒇷𒆷𒀭"
May 2003
Down not across

3·112·29 Posts

Quote:
 Originally Posted by GP2 Does anyone know who this person is, who is finding large new factors for very small Mersenne exponents, independently of GIMPS.
Have you tried contacting SSW?

2017-09-11, 19:34   #314
GP2

Sep 2003

32·7·41 Posts

Quote:
 Originally Posted by xilman Have you tried contacting SSW?
No, but these exponents are a tad larger than the Cunningham project limit.

2017-09-11, 21:26   #315
Dr Sardonicus

Feb 2017
Nowhere

22·1,049 Posts

Quote:
 Originally Posted by GP2 M1489 has a factor: 95909518295775374166321292697000685895150503357477127 (53 digits) It was reported (by who?) to FactorDB on August 17. The remaining 295-digit cofactor is composite, however. Does anyone know who this person is, who is finding large new factors for very small Mersenne exponents, independently of GIMPS.
Quote:
 2017-09-11 kkmrkkblmbrbk F-ECM Factor: 95909518295775374166321292697000685895150503357477127
Post #38 on page 4 of the thread P-1 factoring attempts at smallest-remaining Mersenne numbers with no known factors might give a clue.

2017-09-11, 23:54   #316
GP2

Sep 2003

32×7×41 Posts

Quote:
 Originally Posted by Dr Sardonicus Post #38 on page 4 of the thread P-1 factoring attempts at smallest-remaining Mersenne numbers with no known factors might give a clue.
OK, except these are not exponents with no known factors. In fact, M1471 is now fully factored and M1489 is now 34% factored and the remaining composite cofactor is well within range of NFS. So, if anything, the mystery person might be trying to find "last factors" rather than first factors.

Also, anyone that contributes to these forums would surely manually report any new finds to PrimeNet, which our mystery person is not doing.

2017-09-12, 00:36   #317
VBCurtis

"Curtis"
Feb 2005
Riverside, CA

11×421 Posts

Quote:
 Originally Posted by GP2 ...and M1489 is now 34% factored and the remaining composite cofactor is well within range of NFS.
How do you figure? You said the cofactor is 295 digits, right? So this is either GNFS-295 on the remaining cofactor, or SNFS on the original 1489-bit number.

Both would be world records.

2017-09-12, 00:45   #318
GP2

Sep 2003

32·7·41 Posts

Quote:
 Originally Posted by VBCurtis How do you figure? You said the cofactor is 295 digits, right? So this is either GNFS-295 on the remaining cofactor, or SNFS on the original 1489-bit number. Both would be world records.
Yes the cofactor is 295 digits, or 977 bits.

I either had a brain freeze or I didn't know what I was talking about. Pick the most charitable explanation.

2017-09-12, 01:09   #319
science_man_88

"Forget I exist"
Jul 2009
Dumbassville

26×131 Posts

Quote:
 Originally Posted by VBCurtis How do you figure? You said the cofactor is 295 digits, right? So this is either GNFS-295 on the remaining cofactor, or SNFS on the original 1489-bit number. Both would be world records.
to be fair other than primes the cofactor can't divisors up to a 106 digit number otherwise the composite divisor would have to divide by one of the primes already given or a prime below the last divisor shown.

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