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 2011-01-07, 06:57 #45 ckdo     Dec 2007 Cleves, Germany 2×5×53 Posts M39512171 has a factor: 23887910757239756825399 k = 2039*71597*2070643
 2011-01-10, 18:49 #46 ckdo     Dec 2007 Cleves, Germany 2×5×53 Posts M90012887 has a factor: 439952565941844992833877634700202506740401 k1 = 3*3*5*7*11*19*52177399 k2 = 5*11*71851282747
2011-01-10, 19:14   #47
KingKurly

Sep 2010
Annapolis, MD, USA

101111012 Posts

Quote:
 Originally Posted by ckdo M90012887 has a factor: 439952565941844992833877634700202506740401 k1 = 3*3*5*7*11*19*52177399 k2 = 5*11*71851282747
Goodness, that's a large factor. P-1, I presume?

2011-01-10, 19:53   #48
ckdo

Dec 2007
Cleves, Germany

2·5·53 Posts

Quote:
 Originally Posted by KingKurly Goodness, that's a large factor. P-1, I presume?
TF. First dual 70 bit factors I've seen for an exponent.

2011-01-12, 17:22   #49
lorgix

Sep 2010
Scandinavia

26716 Posts

Quote:
 Originally Posted by ckdo TF. First dual 70 bit factors I've seen for an exponent.
I didn't know that was possible.

2011-01-12, 17:53   #50
Mini-Geek
Account Deleted

"Tim Sorbera"
Aug 2006
San Antonio, TX USA

17·251 Posts

Quote:
 Originally Posted by lorgix I didn't know that was possible.
Why not? There's no reason a number can't have two factors that happen to have the same bit length. There's probably about a 1/4900 (70^(-2)) chance that any particular Mersenne number has two factors that are 70 bits long, so it should be rare, but it's possible.

2011-01-12, 18:27   #51
lorgix

Sep 2010
Scandinavia

3·5·41 Posts

Quote:
 Originally Posted by Mini-Geek Why not? There's no reason a number can't have two factors that happen to have the same bit length. There's probably about a 1/4900 (70^(-2)) chance that any particular Mersenne number has two factors that are 70 bits long, so it should be rare, but it's possible.
I thought it would stop after finding the smaller one.

I wouldn't have been surprised to see a composite factor found by P-1.

2011-01-12, 18:43   #52
axn

Jun 2003

120038 Posts

Quote:
 Originally Posted by Mini-Geek Why not? There's no reason a number can't have two factors that happen to have the same bit length. There's probably about a 1/4900 (70^(-2)) chance that any particular Mersenne number has two factors that are 70 bits long, so it should be rare, but it's possible.
Because prime95 will stop at the first found factor?!

2011-01-12, 19:41   #53
ET_
Banned

"Luigi"
Aug 2002
Team Italia

2×19×127 Posts

Quote:
 Originally Posted by axn Because prime95 will stop at the first found factor?!
Not anymore, IIRC

Luigi

 2011-01-12, 19:59 #54 lorgix     Sep 2010 Scandinavia 3×5×41 Posts Why multiply them, instead of reporting them as they are found?
2011-01-12, 20:48   #55
axn

Jun 2003

47·109 Posts

Quote:
 Originally Posted by ET_ Not anymore, IIRC Luigi
Huh? It used to be that, once upon a time, p95 used to go ahead with TF even if a factor was found, just to make sure that no _smaller_ factor was missed. Then, that was removed. You mean to say that this (mis)feature has been reintroduced?!

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