%I
%S 1,2,3,4,31,34,82,116,120,398,450,566,1216,1478,1776,2379,2816,3492,
%T 3644,7348,8374,8406,9931,13311,15358,16120
%N Numbers k such that 3*5^k  2 is prime.
%C a(27) > 21628.  _Jinyuan Wang_, Dec 14 2019
%t Do[ If[ PrimeQ[ 3*5^n  2 ], Print[ n ] ], {n, 1, 1500} ]
%o (PARI) is(n)=ispseudoprime(3*5^n2) \\ _Charles R Greathouse IV_, Jun 12 2017
%Y Cf. A057916 (3*5^k + 2 is prime).
%K nonn,more
%O 1,2
%A _Robert G. Wilson v_, Nov 17 2000
%E a(20)a(26) from _Jinyuan Wang_, Dec 14 2019
