A133157 Numbers k such that k^2 + k - 41 is prime.

8, 15, 20, 21, 26, 29, 36, 45, 48, 59, 68, 69, 75, 78, 98, 99, 108, 111, 113, 120, 129, 134, 138, 140, 143, 161, 168, 185, 188, 189, 210, 213, 215, 216, 218, 224, 230, 231, 234, 251, 255, 260, 266, 273, 278, 279, 281, 290, 294, 299, 306, 308, 314, 320, 329, 356

Offset: 1

Author

Parthasarathy Nambi, Dec 17 2007

Keywords

• nonn
• easy

Examples

			If k=8, then k^2 + n - 41 = 31 (prime).
If k=99, then k^2 + n - 41 = 9859 (prime).
		

Crossrefs

Cf. A002837.

Programs

Maple

isA133157 := proc(n) isprime(n*(n+1)-41) ; end: for n from 1 to 400 do if isA133157(n) then printf("%d, ",n) ; fi ; od: # R. J. Mathar, Jan 08 2008

Mathematica

Select[Range[7, 400], PrimeQ[ #^2 + # - 41] &] (* Stefan Steinerberger, Dec 24 2007 *)

PARI

is(n)=isprime(n^2+n-41) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

More terms from Stefan Steinerberger, Dec 24 2007

More terms from R. J. Mathar, Jan 08 2008