20140602, 11:32  #1 
Aug 2002
Buenos Aires, Argentina
1446_{10} Posts 
Mersenne number factored (disbelievers are biting elbows)
Using http://www.mersenne.ca/prp.php , I reserved 1000 Mersenne composite numbers in order to perform PRP on the cofactors.
My computer found that: M1304983 = 52199321 x PRP392832 The log from Prime95 is: [Mon Jun 02 04:50:39 2014] M1304983/52199321 is a probable prime! We1: D4B7573A,00000000 It appears to be the largest PRP known from Mersenne numbers. PS: Doing a search on Internet, I found that this PRP was already done: PRP top records Anyway I will continue performing more PRPs on Mersenne number cofactors. Last fiddled with by alpertron on 20140602 at 11:44 
20140602, 20:08  #2 
Feb 2010
Sweden
173 Posts 
It is a pity that this PRP has been reported before, but good luck with the rest. I was doing PRP on cofactors for for a while. Absolutely stupid many would say, but it is funny and anything above the current is a record holder :).

20140602, 20:47  #3 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
23135_{8} Posts 
It would be, in theory. That is, if one knew exactly how far NeverOddOrEven already went. Because you don't know, it is a high risklow return type of research project. The PRP test time goes up, up and up, and the probability of the cofactor being prime goes down and down. You also don't know whether NOOE is still running his tests; if he actually is, then you are virtually attempting to catch up with a power player with significant resources (or in other words, you are not going to catch up).

20140602, 21:01  #4 
Aug 2002
Buenos Aires, Argentina
2·3·241 Posts 
Well, this is not entirely correct, as several new prime factors of Mersenne numbers with exponents lower than 2M are being found every day. So I expect that they have not ran PRP on the new cofactors.

20140602, 21:24  #5 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
7×23×61 Posts 
There is some window in this new pool, I agree.

20140603, 02:14  #6  
Apr 2007
Spessart/Germany
2·3^{4} Posts 
Quote:
Your main problem seems to be of problem of reporting a PRPresult to GIMPS (mersenne.org). As mersenne.ca seems to be 'only' a mirror it doesn't know of the prpresult, because it is not stored at GIMPS. (typically an answer like Quote:
But mersenne.ca works fine if the results are posted there. I assigned 4 hours ago the first 40 available exponents for prptest at range 2M+. the tests needed 3 hours, then I simply copied the resultslines of results.txt (incl. Timestamps) and posted them at mersenne.ca resultpage. It was shown that they were added as 'notprp' to the db and a new list of the available exponents for the same range doesn't show these exponents anymore. So it seems to be only a problem of 'fillingup' the db at mersenne.ca. As Batalov said, it would be helpful if the results of some power players could be added, but on the other hand every new factor 'forces' a new prptest. But I like the idea of a prpdb , I think I will spend some more time for prptest in the next future. greetings, Matthias 

20140603, 07:22  #7 
Feb 2010
Sweden
173 Posts 
When I was looking for PRP, what I did was massive attack of some exponent with TF/Pminus1/ECM until it starts to be unreasonable. Unreasonable is subjective and depends on resources you have. If there were new factors, I was doing a PRP test. If there were no factors, at least I report the TF results to GIMPS (if the expo is unfactored) and Pminus1 results to mersenne.ca, ECM is never a loss. I think the chance for a new PRP is in finding new factors in the range 1.5M3M. That range is still accessible for all methods. I should admit that the best method there is Pminus1, but ECM still kicks some factors.
Last fiddled with by bloodIce on 20140603 at 07:56 
20140603, 11:38  #8 
Aug 2002
Buenos Aires, Argentina
2×3×241 Posts 
In 4 days I cleared more than 1000 exponents in http://www.mersenne.ca and my idea is to have all the exponents below 2M with PRP done. There are still 3000 exponents to be PRP'ed to reach that goal.

20140603, 11:54  #9 
Feb 2010
Sweden
173 Posts 
That is ambitious goal, but achievable. In two weeks you might be done. I may join on over 2M for a while :). However I can do several per day, so my chances are null. Good luck, I would love to see new PRP over the current record.

20140603, 18:45  #10 
Aug 2002
Buenos Aires, Argentina
2·3·241 Posts 
At this moment all exponents below 1911000 were tested.

20140604, 01:22  #11 
Aug 2002
Buenos Aires, Argentina
2·3·241 Posts 
I found that there are some holes in the PRP database on http://www.mersenne.ca. For example, from the link: http://www.mersenne.ca/prp.php?show=...ponent=1911149 we can find a lot of exponents without PRP done, but this range cannot be reserved using the form http://www.mersenne.ca/prp.php?show=...ponent=1911149

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