20201204, 11:29  #1 
Feb 2008
Bray, Ireland
2×3×19 Posts 
Why are small exponents worked on again?
Sorry if I missed the reason for this, but I'm getting a few CERT jobs for really small exponents in the 10M range
e.g. https://www.mersenne.org/report_expo...9448001&full=1 This was factored in 2004. Why was a PRP run on it, then another PRP to DC, then a CERT? Is this just testing to make sure the CERT system works properly? 
20201204, 12:09  #2 
Sep 2006
Brussels, Belgium
11001101111_{2} Posts 
I think it concerns the cofactor primality testing.
There are options to prevent participating in that kind of work which lies outside the primary GIMPS objectives. Jacob 
20201204, 12:40  #3 
Feb 2008
Bray, Ireland
2·3·19 Posts 
I don't mind participating (and it's not like these take any significant time). Just curious about it.

20201204, 14:40  #4  
Feb 2005
Colorado
3·193 Posts 
Quote:


20201204, 15:26  #5  
Feb 2008
Bray, Ireland
114_{10} Posts 
Quote:
And a followup question: If the PRP is positive, how can that large prime be confirmed? And another one: why was a CERT needed if the PRP is DCed? 

20201204, 16:28  #6  
Feb 2005
Colorado
3×193 Posts 
Quote:
B) If the prime is very large, then it can't be confirmed, for now. But the chances of a positive PRP test being composite is very miniscule. C) I noticed this after I posted my first reply, and don't have an answer. Maybe someone else can enlighten us. :) 

20201204, 16:32  #7  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
13·373 Posts 
Quote:
Last fiddled with by kriesel on 20201204 at 16:34 

20201204, 17:28  #8 
Feb 2008
Bray, Ireland
2·3·19 Posts 
OK, thanks.

20201204, 19:57  #9 
P90 years forever!
Aug 2002
Yeehaw, FL
16224_{8} Posts 

20201204, 22:50  #10 
Feb 2008
Bray, Ireland
1110010_{2} Posts 

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