A211409 Numbers n such that (9^n + 4^n)/13 is prime.

3, 5, 7, 11, 17, 19, 41, 53, 109, 167, 2207, 3623, 5059, 5471, 7949, 21211, 32993, 60251

Offset: 1

Author

Robert Price, Feb 09 2013

Keywords

• more
• nonn

Comments

All terms are prime.

The next element, a(19), is greater than 10^5.

Crossrefs

cf. A181141, A128339, A057175, A125956, A187819.

Programs

Mathematica

Select[ Prime[ Range[1, 100000] ], PrimeQ[ (9^# + 4^#)/13 ]& ]

PARI

is(n)=ispseudoprime((9^n+4^n)/13) \\ Charles R Greathouse IV, Jun 13 2017