%I #17 Sep 08 2022 08:46:13
%S 2,3,5,6,27,47,66,77,83,105,197,231,293,702,1692,3021,6270,6897,7733,
%T 14537,15797,21083,21276,28817,65430,111231,137405,141017,185225
%N Numbers m such that (4^m + 23) / 3 is prime.
%C a(30) > 450,000. - _Robert Price_, Oct 04 2018
%e 2 is in the sequence because (4^2 + 23)/3 = 13 is prime.
%e 3 is in the sequence because (4^3 + 23)/3 = 29 is prime.
%t Select[Range[0, 5000], PrimeQ[(4^# + 23)/3] &]
%o (Magma) [n: n in [0..1500] | IsPrime((4^n+23) div 3)];
%Y Cf. similar sequences listed in A261539.
%K nonn,more
%O 1,1
%A _Vincenzo Librandi_, Aug 27 2015
%E a(17)-a(28) from _Robert Price_, Feb 01 2017
%E a(29) from _Robert Price_, Oct 04 2018