mersenneforum.org Riesel Primes k*2^n-1, k<300 [Part II]
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 2007-07-08, 08:26 #2 Cruelty     May 2005 31308 Posts Maybe we should close the original thread to avoid any confusion
 2007-07-08, 13:34 #3 Flatlander I quite division it     "Chris" Feb 2005 England 31×67 Posts k=35 tested to 900,000. Continuing.
 2007-07-09, 06:29 #4 kar_bon     Mar 2006 Germany 2×11×131 Posts status and primes 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)
 2007-07-10, 18:48 #5 Flatlander I quite division it     "Chris" Feb 2005 England 31·67 Posts 105*2^530360-1 is prime.
 2007-07-11, 03:28 #6 gd_barnes     May 2007 Kansas; USA 3×3,449 Posts k=289 now complete to n=470K without a gap 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
 2007-07-12, 06:15 #7 kar_bon     Mar 2006 Germany 2·11·131 Posts 297*2^583464-1 (175643 digits)
 2007-07-13, 23:45 #8 sjtjung     Mar 2006 Columbus, OH 7·11 Posts 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
 2007-07-14, 05:11 #9 gd_barnes     May 2007 Kansas; USA 3·3,449 Posts Status on k=289 and k=2145 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
 2007-07-15, 13:02 #10 Flatlander I quite division it     "Chris" Feb 2005 England 40358 Posts k=251 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? Last fiddled with by Flatlander on 2007-07-15 at 13:18 Reason: Added question.
2007-07-15, 13:59   #11
Kosmaj

Nov 2003

362210 Posts

Quote:
 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.

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