%I #21 Jul 10 2024 03:08:04

%S 1,2,3,4,31,34,82,116,120,398,450,566,1216,1478,1776,2379,2816,3492,

%T 3644,7348,8374,8406,9931,13311,15358,16120,40030,42230,43686,48787,

%U 51696

%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^n-2) \\ _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

%E a(27)-a(31) from _Michael S. Branicky_, Jul 09 2024