A231329 - OEIS

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A231329

Numbers n such that (19^n + 4^n)/23 is prime.

%I #7 Jun 13 2017 14:28:46

%S 7,11,211,14461

%N Numbers n such that (19^n + 4^n)/23 is prime.

%C Conjecture: All terms are prime.

%C a(5) > 10^5.

%t Select[ Prime[ Range[1, 100000] ], PrimeQ[ (19^# + 4^#)/23 ]& ]

%o (PARI) is(n)=ispseudoprime((19^n+4^n)/23) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A227049, A228558, A128075, A229612.

%K hard,nonn,more

%O 1,1

%A _Robert Price_, Nov 07 2013