A229612 - OEIS

%I #7 Jun 13 2017 10:32:27

%S 11,37,107,181,449,457,3583,9133,10139,99689

%N Numbers n such that (19^n + 5^n)/24 is prime.

%C All terms are primes.

%C a(11) > 10^5.

%t k=19; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 9592}]

%o (PARI) is(n)=ispseudoprime((19^n+5^n)/24) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A128075, A228130, A225818.

%K hard,more,nonn

%O 1,1

%A _Robert Price_, Sep 26 2013