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Numbers n such that 6*5^n + 1 is prime.
3

%I #11 Jun 06 2017 14:27:12

%S 0,1,2,3,23,27,33,63,158,278,290,351,471,797,8462,28793,266030

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

%C Primes found and proved by PrimeForm.

%C All terms correspond to verified primes, that is, not merely probable primes. - _Robert Price_, Jan 16 2015

%C a(18) > 3*10^5. - _Robert Price_, Jan 16 2015

%t Select[Range[0, 10000], PrimeQ[6*5^# + 1] &] (* _Robert Price_, Jan 16 2015 *)

%o (PARI) is(n)=ispseudoprime(6*5^n+1) \\ _Charles R Greathouse IV_, Jun 06 2017

%K hard,nonn

%O 1,3

%A _Rick L. Shepherd_, Aug 04 2008

%E a(17) from _Robert Price_, Jan 16 2015