A128350 Numbers k such that (14^k - 5^k)/9 is prime.

2, 151, 673, 709, 2999, 17909, 77213

Offset: 1

Author

Alexander Adamchuk, Feb 27 2007

Keywords

• hard
• more
• nonn

Comments

All terms are primes.

a(8) > 10^5. - Robert Price, Apr 23 2013

Crossrefs

Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128351, A128352, A128353, A128354. Cf. A004061, A082182, A121877, A059802. Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128338, A128339, A128340, A128341, A128342.

Programs

Mathematica

k=14; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n,1,200}]

PARI

is(n)=isprime((14^n-5^n)/9) \\ Charles R Greathouse IV, Feb 17 2017

Extensions

One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), May 01 2008

a(6) and a(7) from Robert Price, Apr 23 2013