A228225 Numbers n such that (17^n + 3^n)/20 is prime.

37, 641, 2521, 7993, 41213

Offset: 1

Author

Robert Price, Aug 16 2013

Keywords

• hard
• more
• nonn

Comments

All terms are primes.

a(6) > 10^5.

Crossrefs

Cf. A128073, A224507, A128075, A227046.

Programs

Mathematica

k=17; Do[ p=Prime[n]; f=(3^p+k^p)/(k+3); If[ PrimeQ[f], Print[p]], {n, 1, 9592} ]

PARI

is(n)=ispseudoprime((17^n+3^n)/20) \\ Charles R Greathouse IV, Jun 13 2017