Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.
%I #29 Nov 29 2023 10:41:06
%S 1,3,5,9,15,33,41,335,443,671,1197,1355,2247,2639,117293,191099
%N Numbers k such that 4^k + 9 is prime.
%C The next terms are > 250000. - _Robert Price_, Oct 05 2015
%C Contains exactly the halved even terms of A057196.
%e For k = 15, 4^15 + 9 = 1073741833 is prime.
%t Select[Range[0, 5000], PrimeQ[4^# + 9] &]
%o (Magma) [n: n in [0..700] | IsPrime(4^n+9)]; // _Vincenzo Librandi_, Oct 06 2015
%o (PARI) is(n)=ispseudoprime(4^n+9) \\ _Charles R Greathouse IV_, Jun 06 2017
%Y Cf. A057196, A089437 (similar sequence).
%K nonn,more
%O 1,2
%A _Vincenzo Librandi_, Oct 01 2012
%E a(15)-a(16) derived from A057196 by _Robert Price_, Oct 05 2015