A261579 - OEIS

%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