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Old 2010-05-07, 15:12   #5
mdettweiler
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Aug 2007
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Quote:
Originally Posted by Mini-Geek View Post
I was just thinking about this again:
http://www.mersenneforum.org/showthread.php?t=12591 (looking for twin primes by searching the 'other side', i.e. swapping -1 and +1, of a known prime)
But the top 5000 list has so many different prime forms, and is only accessible through text or HTML (both of which would not be terribly easy to extract the essentials from) it'd be non-trivial to get a list of candidates to test. So then I thought of NPLB: tons of primes, all in the form k*2^n-1, all in a central DB that can pick out the k and n for me. Easy!
I'd like to apply this idea to the full list of NPLB primes. NPLB has found 6604 (as of this writing) primes for -1, and I'd like to find if any of those have a twin on the +1 side. I could try to download all the pages and extract the k and n, but I figured it'd be easier to ask one of you with DB access to dump the list for me. (consider it requested preferably in the NewPGen format of one "k n" per line)
6604 candidates of all sizes before any sieving is sure to reduce to a handful of testable candidates. TBH I'm not too hopeful that such a twin does exist, but it'd be such an easy check it's almost a waste to look for new primes to find their twins before checking old primes to see if they have twins.
If you want I can dump the DB's list for you rather easily, but it sounds like Karsten's list might be even better, since it contains ALL known Riesel primes rather than just NPLB's. If you'd still like to get the DB's list, though, let me know.
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