Riesel Primes k*2^n-1, k<300 [Part II]

[Kosmaj]

The original k<300 thread was started in December 2003 and contains almost 600 posts. It is a great source of information about work already done, but I think we need a new thread for new posts.

The first post of the original thread contains some useful links to software used for primality search and to several stats pages listing all found primes. I'll continue to update that post, but almost all information is available on our web site too.

Please post your new k<300 reservations, and your comments and observatons in this thread.

The latest search status, updated frequently, can be found here.

Thanks,
Kosmaj:

[Cruelty]

Maybe we should close the original thread to avoid any confusion

[Flatlander]

k=35 tested to 900,000. Continuing.

[kar_bon]

k=209 llr at 704 k: 2 new primes:
209*2^692692-1 and 209*2^675232-1 (last prime at 60k!!!).

k=297 llr still at 581k (work next and let rest 209 a while)

[Flatlander]

105*2^530360-1 is prime.

[gd_barnes]

One of the cores on my high-speed dual machine has now completed k=289 for the range of n=260K to 400K. The other core that I've temporarily stopped for other activities had previously completed the range of n=400K to n=470K so this completes it up to n=470K with no gaps. No more primes have been found since n=90201.

This leaves a remaining gap for k=289 of n=470K to n=501991. I have now re-started the other core and it will run all the way up to n=520K to complete filling of the gap and confirm some prior testing.


Gary

[kar_bon]

297*2^583464-1 (175643 digits)

[sjtjung]

Brief update regarding new issue...

207 is at 583k and pausing to work on 31.
31 is on hold at 567k. Currently working on 800k and up to race with Benson.
567k-800k gap will be filled soon.

-Steven

[gd_barnes]

I'm now complete on k=289 up to n=485K. Still no additional primes.

On k=2145, I've completed my own testing and am now testing from some sieve files given to me by Curtis. I'm now complete up to n=180K. Since my last status of n=120K, all previous primes listed on the summary site are correct and there were no additional primes found.


Gary

[Flatlander]

Reserving k = 251 from 545,000.
I'll push this low weight a bit higher; only about 10.5 candidates per 1000.


Just a thought. Is it possible for a k to stop producing primes once it has produced one or more?

[Kosmaj]

Originally Posted by Flatlander

Just a thought. Is it possible for a k to stop producing primes once it has produced one or more?

No, I think it's proven that if k has a prime for one n, then there are primes for infinitely many. But the gaps between primes can be large. See for example k=253 and k=101.