%I
%S 1,2,4,10,19,32,40,146,566,2054,9967,62639,87814,141092
%N Numbers n such that 4^n + 13 is prime.
%C Numbers of the form 4^n+k (for n>0) are never primes when k is even (obviously) or when k == 1 (mod 6): in the last case, in fact, (3+1)^n + 6*h1 is divisible by 3.  _Bruno Berselli_, Oct 06 2015
%t Select[Range[4000], PrimeQ[4^# + 13] &]
%o (MAGMA) [n: n in [0..2000]  IsPrime(4^n+13)];
%o (PARI) is(n)=ispseudoprime(4^n+13) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y Cf. A104067.
%Y Cf. numbers n such that 4^n+k is prime: A089437 (k=3), A217349 (k=7), A217350 (k=9), this sequence (k=13), A253773 (k=15), A253774 (k=19), A262345 (k=21), A204388 (k=25), A262969 (k=27), A262971 (k=31), A262972 (k=33).
%K nonn,more
%O 1,2
%A _Vincenzo Librandi_, Jan 12 2015
%E a(11)a(14) derived from A102634 by _Robert Price_, Sep 06 2015
