Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #18 Jul 14 2023 11:55:26
%S 3,7,11,47,81,95,107,179,233,243,947,2817,2859,3233,7563,11307,218615,
%T 225587
%N Numbers k such that 8^k - 9 is prime.
%C All terms are equal to 1/3 of the multiples of 3 in A059610.
%C Naturally these numbers are odd since 8^(2n)-9 = (8^n-3)(8^n+3) is composite. - _Bruno Berselli_, Oct 04 2012
%t Select[Range[10000], PrimeQ[8^# - 9] &]
%o (PARI) is(n)=ispseudoprime(8^n-9) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A059610, A217356, A217382.
%K nonn,more
%O 1,1
%A _Vincenzo Librandi_, Oct 03 2012
%E a(17)-a(18) using A059610 from _Michael S. Branicky_, Jul 14 2023