%I #20 Apr 08 2021 07:19:20
%S 1,2,9,24,42,74,221,620,14064,36697,152048,384558
%N Numbers k such that 14^k + 3 is prime.
%e 1 is a term since 14^1 + 3 = 17 is a prime.
%t Do[ If[ PrimeQ[ 14^n + 3], Print[n]], {n, 0, 200000}]
%o (PARI) is(n)=isprime(14^n + 3)
%Y Cf. A339924.
%K nonn,more
%O 1,2
%A _Paul Bourdelais_, Dec 23 2020
%E a(12) corresponds to a probable prime discovered by _Paul Bourdelais_, Jan 06 2021