A217380 Numbers k such that 8^k - 7 is prime.

13, 661, 773, 833, 4273, 40613, 302913

Offset

1,1

Comments

All terms are equal to 1/3 of the multiples of 3 in A059609.

Naturally these numbers are odd since (9-1)^(2n)-7 is divisible by 3. - Bruno Berselli, Oct 04 2012

Links

Table of n, a(n) for n=1..7.

Mathematica

Select[Range[4000], PrimeQ[8^# - 7] &]

Prog

(PARI) is(n)=ispseudoprime(8^n-7) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A059609, A217353, A217356.

Sequence in context: A143734 A362898 A316331 * A068232 A363864 A092547

Adjacent sequences: A217377 A217378 A217379 * A217381 A217382 A217383

Keyword

nonn,more

Author

Vincenzo Librandi, Oct 02 2012

Extensions

a(7) using A059609 from Michael S. Branicky, Sep 15 2024

Status

approved