A128352 Numbers k such that (17^k - 5^k)/12 is prime.

5, 7, 17, 23, 43, 71, 239, 733, 1097

Offset: 1

Author

Alexander Adamchuk, Feb 27 2007

Keywords

• nonn
• hard
• more

Comments

All terms are primes.

a(10) > 10^5. - Robert Price, Jun 11 2013

Crossrefs

Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128351, A128353, A128354.

Cf. A004061, A082182, A121877, A059802.

Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128338, A128339, A128340, A128341, A128342.

Programs

Mathematica

k=17; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,100}]

PARI

is(n)=isprime((17^n-5^n)/12) \\ Charles R Greathouse IV, Feb 17 2017