A224501 Numbers n such that (11^n + 4^n)/15 is prime.

7, 53, 67, 71, 443, 26497

Offset: 1

Author

Robert Price, Apr 08 2013

Keywords

• hard
• nonn
• more

Comments

All terms are prime.

a(7) > 10^5.

Crossrefs

Cf. A057178, A128341, A181141, A187819, A217095.

Programs

Mathematica

Select[ Prime[ Range[1, 100000] ], PrimeQ[ (11^# + 4^#)/15 ]& ]

PARI

is(n)=ispseudoprime((11^n+4^n)/15) \\ Charles R Greathouse IV, Jun 06 2017