POST LOTS AND LOTS OF PRIMES HERE - Page 168

VBCurtis · 2017-08-05, 15:58

Quote:

Originally Posted by paulunderwood

There seems to be a discrepancy:

http://primes.utm.edu/primes/page.ph...3806&deleted=1

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.

VBCurtis · 2017-08-05, 17:02

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.

Trilo · 2017-08-06, 07:53

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.

amphoria · 2017-09-18, 09:42

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

Thomas11 · 2017-09-18, 09:52

Quote:

Originally Posted by amphoria

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

Congratulations on this very nice pair, Dave!

Kosmaj · 2017-09-20, 09:04

Hi Dave, Congrats on nice primes!

Congrats also to Trilo on his pair.

Chair Zhuang · 2017-12-13, 20:19

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

amphoria · 2017-12-14, 14:48

Quote:

Originally Posted by Chair Zhuang

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

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.

Chair Zhuang · 2017-12-15, 22:58

Thank you! amphoria. I am a new member.

VBCurtis · 2017-12-18, 22:22

229*2^2581111-1 is prime. 776995 digits.

Thomas11 · 2017-12-30, 10:40

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

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2017-08-05, 17:02	#1839
VBCurtis "Curtis" Feb 2005 Riverside, CA 4737₁₀ Posts	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.

2017-08-06, 07:53	#1840
Trilo "W. Byerly" Aug 2013 1423*2^2179023-1 103 Posts	Since we are on the subject of consecutive large primes with small n gaps, here is a pair I found a while back: 14232^2179023-1 14232^2178363-1 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.

2017-09-18, 09:42	#1841
amphoria "Dave" Sep 2005 UK 5330₈ Posts	492^4360869-1 (1312755 digits) 492^4365175-1 (1314051 digits)

2017-09-20, 09:04	#1843
Kosmaj Nov 2003 2×1,811 Posts	Hi Dave, Congrats on nice primes! Congrats also to Trilo on his pair.

2017-12-13, 20:19	#1844
Chair Zhuang Dec 2017 2·5 Posts	How long did your computer take to test it? And how many GHz has your computer?

2017-12-15, 22:58	#1846
Chair Zhuang Dec 2017 1010₂ Posts	Thank you! amphoria. I am a new member.

2017-12-18, 22:22	#1847
VBCurtis "Curtis" Feb 2005 Riverside, CA 3×1,579 Posts	229*2^2581111-1 is prime. 776995 digits.

2017-12-30, 10:40	#1848
Thomas11 Feb 2003 2²×3²×53 Posts	From our 7th drive: 27152^1629931-1 (490662 digits) 27152^1640137-1 (493734 digits)