20170805, 15:58  #1838  
"Curtis"
Feb 2005
Riverside, CA
10605_{8} Posts 
Quote:


20170805, 17:02  #1839 
"Curtis"
Feb 2005
Riverside, CA
4485_{10} Posts 
A doublecheck on my i7haswell (linuxsllr64) confirms compositeness. Next time I see the machine that found this "prime", I'll make sure I didn't transpose digits when I copied down the exponent; but that's pretty unlikely with 3 consecutive zeros.

20170806, 07:53  #1840 
"W. Byerly"
Aug 2013
1423*2^21790231
62_{16} Posts 
Since we are on the subject of consecutive large primes with small n gaps, here is a pair I found a while back:
1423*2^21790231 1423*2^21783631 The most interesting thing about this pair is that the k value has very low nash weight of just 309. It would be interesting if we could define a function that takes in the gap size, nash weight, and n size and outputs another number representing the "rarity" of the pair. 
20170918, 09:42  #1841 
"Dave"
Sep 2005
UK
2·19·73 Posts 
49*2^43608691 (1312755 digits)
49*2^43651751 (1314051 digits) 
20170918, 09:52  #1842 
Feb 2003
1,907 Posts 

20170920, 09:04  #1843 
Nov 2003
2×1,811 Posts 
Hi Dave, Congrats on nice primes!
Congrats also to Trilo on his pair. 
20171213, 20:19  #1844 
Dec 2017
2·5 Posts 
How long did your computer take to test it? And how many GHz has your computer?

20171214, 14:48  #1845 
"Dave"
Sep 2005
UK
5326_{8} Posts 
The first took 6300s to test on a 3.6 GHz Ivy Bridge CPU. The second was tested on a 2.9 GHz Haswell CPU. I currently don't have access to the timing but given that it has AVX2, I would expect it to be at least as fast as the other despite the lower clock speed.

20171215, 22:58  #1846 
Dec 2017
2·5 Posts 
Thank you! amphoria. I am a new member.

20171218, 22:22  #1847 
"Curtis"
Feb 2005
Riverside, CA
3·5·13·23 Posts 
229*2^{2581111}1 is prime. 776995 digits.

20171230, 10:40  #1848 
Feb 2003
1,907 Posts 
From our 7th drive:
2715*2^16299311 (490662 digits) 2715*2^16401371 (493734 digits) 
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