A128339 Numbers k such that (9^k + 5^k)/14 is prime.

3, 5, 13, 17, 43, 127, 229, 277, 6043, 11131, 11821

Offset

1,1

Comments

All terms are primes.

a(12) > 10^5. - Robert Price, Dec 26 2012

Links

Table of n, a(n) for n=1..11.

Mathematica

k=9; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

Prog

(PARI) is(n)=isprime((9^n+5^n)/14) \\ Charles R Greathouse IV, Feb 17 2017
(Magma) [n: n in [3..300] |IsPrime((9^n + 5^n) div 14)]; // Vincenzo Librandi, Nov 02 2018

Crossrefs

Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128338, A128340, A128341, A128342, A128343. Cf. A004061, A082182, A121877, A059802. Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128351, A128352, A128353, A128354.

Sequence in context: A089996 A307512 A080076 * A147506 A360801 A282960

Adjacent sequences: A128336 A128337 A128338 * A128340 A128341 A128342

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 27 2007

Extensions

3 more PRP terms from Sean A. Irvine, Oct 01 2009

Status

approved