A187805 Numbers n such that (7^n + 6^n)/13 is prime.

3, 53, 83, 487, 743

Offset: 1

Author

Robert Price, Jan 06 2013

Keywords

• more
• hard
• nonn

Comments

All terms are prime.

a(6) > 10^5

Crossrefs

Cf. A181141, A128336, A128337.

Programs

Mathematica

Select[ Prime[ Range[100000] ], PrimeQ[ (7^# + 6^#)/13 ]& ]

PARI

is(n)=ispseudoprime((7^n+6^n)/13) \\ Charles R Greathouse IV, Feb 17 2017