A204323 Numbers n such that 4*7^n + 1 is prime.

0, 1, 2, 3, 6, 7, 10, 11, 17, 38, 65, 133, 150, 502, 537, 894, 6442, 16474, 23642, 40894, 94133, 101335, 135737, 224437, 254621, 266782

Offset

1,3

Links

Table of n, a(n) for n=1..26.

Mathematica

Select[Range[0, 2000], PrimeQ[4*7^#+1]&]

Prog

(PARI) is(n)=ispseudoprime(4*7^n+1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A026443 A345251 A349257 * A278965 A032858 A181498

Adjacent sequences: A204320 A204321 A204322 * A204324 A204325 A204326

Keyword

nonn

Author

José María Grau Ribas, Jan 14 2012

Extensions

a(17)-a(26) from Predrag Kurtovic, May 24 2015

Status

approved