A186112 - OEIS

%I #15 Feb 20 2023 07:51:43

%S 1,2,4,6,7,8,11,15,26,29,50,66,122,225,272,275,308,390,992,1201,2520,

%T 15812,17419,29328,41852

%N Numbers k such that 3*6^k + 1 is prime.

%C The primes produced by these values of n are in A186105.

%e 15 is in the sequence because 3*6^15+1=1410554953729 is prime.

%o (PARI) select(n->ispseudoprime(3*6^n+1),vector(10^4,i,i)) \\ _Charles R Greathouse IV_, Feb 13 2011

%o (PFGW) ABC2 3*6^$a+1

%o a: from 1 to 50000

%K nonn

%O 1,2

%A _Gilbert Mozzo_, Feb 12 2011

%E a(14), a(15), a(17) added by _D. S. McNeil_, Feb 12 2011

%E a(20)-a(25) from _Charles R Greathouse IV_, Feb 13 2011 to Feb 14 2011