A128351 Numbers k such that (16^k - 5^k)/11 is prime.

7, 13, 109, 139, 967, 60013, 97613

Offset: 1

Author

Alexander Adamchuk, Feb 27 2007

Keywords

• hard
• more
• nonn

Comments

All terms are primes.

a(8) > 10^5. - Robert Price, Jul 03 2013

Crossrefs

Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128352, A128353, A128354, A004061, A082182, A121877, A059802, A057171, A082387, A122853, A128335-A128342.

Programs

Mathematica

k=16; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,100}]

PARI

is(n)=isprime((16^n-5^n)/11) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

a(6)-a(7) from Robert Price, Jul 03 2013