[QUOTE=paulunderwood;464895]There seems to be a discrepancy:

[url]http://primes.utm.edu/primes/page.php?id=123806&deleted=1[/url][/QUOTE]

Hrmm. Both were found by the same machine, a new low-end i3 desktop that hasn't had its case opened. Thanks for pointing this out- I'll run a double-check on another machine myself, as the compositeness test you linked indicated some roundoff errors.

A double-check on my i7-haswell (linux-sllr64) 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.

Since we are on the subject of consecutive large primes with small n gaps, here is a pair I found a while back:

1423*2^2179023-1
1423*2^2178363-1

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.

49*2^4360869-1 (1312755 digits)
49*2^4365175-1 (1314051 digits)

[QUOTE=amphoria;468018]49*2^4360869-1 (1312755 digits)
49*2^4365175-1 (1314051 digits)[/QUOTE]

Congratulations on this very nice pair, Dave! :banana:

Hi Dave, Congrats on nice primes!

Congrats also to Trilo on his pair.

How long did your computer take to test it? And how many GHz has your computer?

[QUOTE=Chair Zhuang;473953]How long did your computer take to test it? And how many GHz has your computer?[/QUOTE]

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.

Thank you! amphoria. I am a new member.

229*2[SUP]2581111[/SUP]-1 is prime. 776995 digits.

From our 7th drive:
2715*2^1629931-1 (490662 digits)
2715*2^1640137-1 (493734 digits)