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A133157
Numbers k such that k^2 + k - 41 is prime.
1
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
1,1
EXAMPLE
If k=8, then k^2 + n - 41 = 31 (prime).
If k=99, then k^2 + n - 41 = 9859 (prime).
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 *)
PROG
(PARI) is(n)=isprime(n^2+n-41) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Cf. A002837.
Sequence in context: A160524 A161541 A247081 * A014544 A237610 A122754
KEYWORD
nonn,easy
AUTHOR
Parthasarathy Nambi, Dec 17 2007
EXTENSIONS
More terms from Stefan Steinerberger, Dec 24 2007
More terms from R. J. Mathar, Jan 08 2008
STATUS
approved