%I #42 Oct 31 2024 11:23:35
%S 1,47,91,64655
%N Numbers k such that 8^k + 5 is prime.
%C All terms are 1/3 of the terms of A059242 that are multiples of 3.
%C No more terms <= 10^5. - _Tyler NeSmith_
%t Select[Range[1000], PrimeQ[8^# + 5] &]
%o (Magma) [n: n in [0..1000] | IsPrime(8^n + 5)];
%o (PARI) is(n)=ispseudoprime(8^n+5) \\ _Charles R Greathouse IV_, Feb 20 2017
%Y Cf. A059242, A217354.
%K nonn,hard,more
%O 1,2
%A _Vincenzo Librandi_, Oct 02 2012
%E a(4) from _Tyler NeSmith_, Jan 19 2021