20070115, 12:13  #1 
Jun 2003
11265_{8} Posts 
Left over Sophie Germain primes?
Now that the twin prime has been found, can some one just run thru all the 1 primes found and test if k*2^(n+1)1 is also prime? Eventhough it is a long shot, who knows, there just might be a Sophie Germain prime lurking there!

20070115, 12:30  #2  
"Robert Gerbicz"
Oct 2005
Hungary
1419_{10} Posts 
Quote:
Járai has used a combined sieve, I think for k*2^n+1 and k*2^(n+1)1, that's the reason why their k value's are so large (15 digits), and they've found record twin and Sophie Germain primes for n=171960. Last fiddled with by R. Gerbicz on 20070115 at 12:30 

20070115, 12:42  #3 
Jun 2003
4,789 Posts 
I am not suggesting that the present search continue to look for SG, but merely to take the currently found primes (IIRC, < 1000) and just see if they yield any SG primes. An opportunistic longshot rather than a determined effort.
Last fiddled with by axn on 20070115 at 12:44 Reason: spelling 
20070115, 12:57  #4  
"Robert Gerbicz"
Oct 2005
Hungary
3×11×43 Posts 
Quote:
You can double your chance: if k*2^n1 is prime then check k*2^(n+1)1 but also check k*2^(n1)1. And you can also sieve up to say 10^7 or something like that, because by large probability these numbers has got a small prime factor. Then do PRP test for the survivors. 

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