20070708, 00:09  #1 
Nov 2003
7046_{8} Posts 
Riesel Primes k*2^n1, k<300 [Part II]
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: Last fiddled with by Kosmaj on 20100920 at 05:21 
20070708, 08:26  #2 
May 2005
2^{2}·11·37 Posts 
Maybe we should close the original thread to avoid any confusion

20070708, 13:34  #3 
I quite division it
"Chris"
Feb 2005
England
31×67 Posts 
k=35 tested to 900,000. Continuing.

20070709, 06:29  #4 
Mar 2006
Germany
2^{4}×3×61 Posts 
status and primes
k=209 llr at 704 k: 2 new primes:
209*2^6926921 and 209*2^6752321 (last prime at 60k!!!). k=297 llr still at 581k (work next and let rest 209 a while) 
20070710, 18:48  #5 
I quite division it
"Chris"
Feb 2005
England
31·67 Posts 
105*2^5303601 is prime.

20070711, 03:28  #6 
May 2007
Kansas; USA
3^{3}·17·23 Posts 
k=289 now complete to n=470K without a gap
One of the cores on my highspeed 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 restarted 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 
20070712, 06:15  #7 
Mar 2006
Germany
2^{4}·3·61 Posts 
297*2^5834641 (175643 digits)

20070713, 23:45  #8 
Mar 2006
Columbus, OH
77_{10} 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. 567k800k gap will be filled soon. Steven 
20070714, 05:11  #9 
May 2007
Kansas; USA
3^{3}×17×23 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 
20070715, 13:02  #10 
I quite division it
"Chris"
Feb 2005
England
31·67 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 20070715 at 13:18 Reason: Added question. 
20070715, 13:59  #11 
Nov 2003
2×1,811 Posts 
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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