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Numbers n such that 5*6^n + 1 is prime.
5

%I #9 Sep 11 2014 15:13:04

%S 1,2,4,17,136,147,203,590,754,964,970,1847,2031,2727,2871,5442,7035,

%T 7266,11230,23307,27795,34152,42614,127206,133086

%N Numbers n such that 5*6^n + 1 is prime.

%C a(26) > 2*10^5.

%t Do[ If[ PrimeQ[5*6^n + 1], Print[n]], {n, 0, 200000}]

%o (PARI)

%o for(n=0,2*10^5,if(ispseudoprime(5*6^n+1),print1(n,", "))) \\ _Derek Orr_, Sep 10 2014

%Y Cf. A079906.

%K nonn,hard,more

%O 1,2

%A _Robert Price_, Sep 10 2014