A217383 Numbers k such that 8^k - 9 is prime.

3, 7, 11, 47, 81, 95, 107, 179, 233, 243, 947, 2817, 2859, 3233, 7563, 11307, 218615, 225587, 1160027

Offset: 1

Author

Vincenzo Librandi, Oct 03 2012

Keywords

• nonn
• more

Comments

All terms are equal to 1/3 of the multiples of 3 in A059610.

Naturally these numbers are odd since 8^(2n)-9 = (8^n-3)(8^n+3) is composite. - Bruno Berselli, Oct 04 2012

Crossrefs

Cf. A059610, A217356, A217382.

Programs

Mathematica

Select[Range[10000], PrimeQ[8^# - 9] &]

PARI

is(n)=ispseudoprime(8^n-9) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(17)-a(18) using A059610 from Michael S. Branicky, Jul 14 2023

a(19) using A059610 from Michael S. Branicky, Apr 23 2025