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%I #7 Jun 06 2017 14:33:20
%S 7,53,67,71,443,26497
%N Numbers n such that (11^n + 4^n)/15 is prime.
%C All terms are prime.
%C a(7) > 10^5.
%t Select[ Prime[ Range[1, 100000] ], PrimeQ[ (11^# + 4^#)/15 ]& ]
%o (PARI) is(n)=ispseudoprime((11^n+4^n)/15) \\ _Charles R Greathouse IV_, Jun 06 2017
%Y Cf. A057178, A128341, A181141, A187819, A217095.
%K hard,nonn,more
%O 1,1
%A _Robert Price_, Apr 08 2013