20071109, 02:30  #34 
Nov 2003
2×1,811 Posts 

20071226, 19:21  #37  
A Sunny Moo
Aug 2007
USA (GMT5)
14151_{8} Posts 
Quote:


20071226, 21:46  #38 
Nov 2003
3622_{10} Posts 
Cruelty
We can sustain this one, still 4th, but not the next larger one. 
20071227, 00:29  #39 
May 2005
2·809 Posts 

20080117, 00:31  #40 
Nov 2003
3622_{10} Posts 
Congrats to Richard (L185) on a huge prime
3139*2^33219051 only 3 digits shy of one million digits! He found the 9th SoB prime in 2005 (4847*2^3321063+1, 999744 digits) and is currently ranked 14th person by score. Last fiddled with by Kosmaj on 20080117 at 00:31 
20080202, 15:09  #41 
Oct 2007
3^{2}·11 Posts 
.
Prof. Cooper found another very large prime:
7 * 2^3015762+1 (907836 digits). By the way, can I somewhere find an overview how fast the different forms of numbers can be tested at the moment (for a example a comparison of the forms k*2^n1, k*2^n+1, k*b^n+/1)? Last fiddled with by Retep on 20080202 at 15:10 
20080203, 14:03  #42 
Nov 2003
2×1,811 Posts 
Yes, that's his largest prime after two Mersennes.
We are now waiting to see is it a Fermat or a GF divisor, I'm sure he is now working on those tests. As for the processing speed, when b=2, both 1 and +1 are about the same for the given k. When b>2 it's much slower (except, of course when b is a power of 2). 
20080308, 23:32  #43 
May 2005
2×809 Posts 
4*3^3118351 (148784 digits)
Attached is a list of primes for k=4 b=3. 
20080310, 04:55  #44 
Nov 2003
2×1,811 Posts 
Cruelty
Congrats on a nice effort and a nice prime! I remember that prof. Iskra had a special speedup for a^2*3^n+1, (n odd) and found a number of large primes. I just found that his article is now available free of charge! The Corollary 2.3 won't be difficult to implement uisng GMP... 
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