mersenneforum.org A question about ecm's top100 (novice)
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 2005-05-27, 17:23 #1 [Leo_01]   May 2005 Lyon 108 Posts A question about ecm's top100 (novice) Hello, I found this factor: Run 12 out of 940: Using B1=1000000, B2=839549779, polynomial Dickson(3), sigma=3995282753 Step 1 took 77500ms Step 2 took 38490ms ********** Factor found in step 2: 71714208610579105792540408011003007751948902382471874795499986007319 Found composite factor of 68 digits: 71714208610579105792540408011003007751948902382471874795499986007319 Composite cofactor 6587259828147373028882426117244546464250110605851985519710308763002069923 has 73 digits It's a factor of p20005 and is composite :-(. The ECMNET project maintained a list of all the factors found with GMP-ECM. But is it necessary that this factor is prime? or any factor found with GMP-ECM (composite or prime) is valid? Thanks you in advance. Alex Sorry for my bad english.
 2005-05-27, 17:33 #2 VJS     Dec 2004 13×23 Posts Yes it has to be a prime factor.
2005-05-27, 17:38   #3
ET_
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"Luigi"
Aug 2002
Team Italia

17×283 Posts

Quote:
 Originally Posted by [Leo_01] Found composite factor of 68 digits: 71714208610579105792540408011003007751948902382471874795499986007319 Composite cofactor 6587259828147373028882426117244546464250110605851985519710308763002069923 has 73 digits
Composite factor of 68 digits splits as
221327431219133172774525501130163 * 324018619000623911696302737119750413

while composite cofactor of 73 digits splits as
28242483789997587424530225403013 * 233239394846721295985738738334629297112071

Luigi

 2005-05-27, 18:03 #4 [Leo_01]   May 2005 Lyon 23 Posts thank you :-)

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