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Kosmaj 2007-11-09 02:30

Posts about k*10^n-1 moved to [URL=""]another thread[/URL].

Please post new messages on this topic there.

gd_barnes 2007-12-14 21:18

New Conjectures 'R Us prime search effort
Hi all...

Come check out the new "Conjectures 'R Us" prime search effort [URL=""]here[/URL]. There's plenty of bases and k's for everyone to search and have fun.


Cruelty 2007-12-26 19:13

Check [URL=""]this[/URL] out... if this is part of primegrid, then we will fall to #5 I guess... (in terms of score)

mdettweiler 2007-12-26 19:21

[quote=Cruelty;121569]Check [URL=""]this[/URL] out... if this is part of primegrid, then we will fall to #5 I guess... (in terms of score)[/quote]
I don't see PrimeGrid in the prover code...though I can't imagine why someone would be searching for Woodall primes outside of PrimeGrid (since they would be duplicating a lot of work, especially the sieving work). It's roughly in the range that PrimeGrid is searching, though, so I wouldn't be surprised if it was a PrimeGrid thing, just that the finder forgot to include PrimeGrid in his prover code. (I'm sure if that's the case, though, the Prime Pages people will fix it.)

Kosmaj 2007-12-26 21:46


We can sustain this one, still 4th, but not the next larger one.

Cruelty 2007-12-27 00:29

[QUOTE=Kosmaj;121588]We can sustain this one, still 4th, but not the next larger one.[/QUOTE]That is why we are all waiting for your k=7 prime :tu: + some other megabit primes are long overdue from me :wink:

Kosmaj 2008-01-17 00:31

Congrats to Richard (L185) on a huge prime

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.

Retep 2008-02-02 15:09

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^n-1, k*2^n+1, k*b^n+/-1)?

Kosmaj 2008-02-03 14:03

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).

Cruelty 2008-03-08 23:32

1 Attachment(s)
4*3^311835-1 (148784 digits)
Attached is a list of primes for k=4 b=3.

Kosmaj 2008-03-10 04:55


Congrats on a nice effort and a nice prime!

I remember that prof. Iskra had a special speed-up for
a^2*3^n+1, (n odd)

and found a number of large primes. I just found that [URL=""]his article[/URL] is now available free of charge! The Corollary 2.3 won't be difficult to implement uisng GMP...

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