20091020, 13:52  #1 
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
4,271 Posts 
idea for twin prime searching
Has anybody tried taking a list of primes from the top 5000, or other lists of primes, and searching the opposite side for a prime? (e.g. #500 is currently 2951*2^8528181, so sieve and if necessary LLR 2951*2^852818+1; in this case it has small factors, just an example) It could potentially be a very easy way to find a twin prime pair where one side is already known.
Last fiddled with by MiniGeek on 20091020 at 13:54 
20091020, 15:55  #2 
I quite division it
"Chris"
Feb 2005
England
100000011101_{2} Posts 
I tried that a couple of years ago and got part way through the list. (From the bottom up.)
edit: Check out the "Other Primes" thread at NPLB, from post 20. Last fiddled with by Flatlander on 20091020 at 16:08 
20091020, 17:59  #3 
Jan 2009
Ireland
2×3×31 Posts 
thought of this earlier in the year,but came to the conclusion that someone would of done this already.thought it would be logical for someone that's searching for a twin prime to test the opposite side of known primes.

20091021, 14:53  #4  
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
4271_{10} Posts 
Quote:
Quote:
I'd think that too, but you never know unless you ask. Maybe everybody who's thought of this ignored it for the same reasons, and so an easy twin prime is still hiding in plain sight! Last fiddled with by MiniGeek on 20091021 at 15:01 

20091021, 17:05  #5 
I quite division it
"Chris"
Feb 2005
England
2077_{10} Posts 
I'mm 99% sure anything I tested would be off the list now. I think it was longer than 2 years ago; I don't think I got near k*2^4000001.

20091022, 04:13  #6 
Dec 2006
Anchorage, Alaska
2·3·13 Posts 
You might also go to the 3 and not just the opposite side?
ie 253*2^50001 and 253*2^50003 or some such thing Still a twin! 
20091023, 17:40  #7 
Jul 2009
2^{2} Posts 
The problem with the 3 is I don't think there's an easy primality test for k2^n3. That's why all our searches are for +1 and 1 is people have figured out "easy" tests to show whether those are prime. For numbers of random form the best we can do is show it's probably prime.

20091023, 19:46  #8 
Sep 2004
533_{10} Posts 
The ones on the list are way to big for primo as well. It still would be an interesting project to show they are prp's though.

20110130, 00:18  #9  
May 2004
New York City
5·7·11^{2} Posts 
Quote:
I have an idea, but it's just germinating. 

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