A128336 Numbers k such that (6^k + 5^k)/11 is prime.

3, 5, 17, 397, 409, 643, 1783, 2617, 4583, 8783

Offset

1,1

Comments

All terms are primes.

No other terms less than 100000. - Robert Price, May 11 2012

Links

Table of n, a(n) for n=1..10.

Mathematica

k=6; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

Prog

(PARI) forprime(p=3, 1e4, if(ispseudoprime((6^p+5^p)/11), print1(p", "))) \\ Charles R Greathouse IV, Jul 16 2011

Crossrefs

Cf. A057171, A082387, A122853, A128335, A128337, A128338, A128339, A128340, A128341, A128342, A128343, A004061, A082182, A121877, A059802, A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128351, A128352, A128353, A128354.

Sequence in context: A100270 A016045 A349121 * A278735 A094487 A007516

Adjacent sequences: A128333 A128334 A128335 * A128337 A128338 A128339

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 27 2007

Extensions

a(7)-a(9) from Alexander Adamchuk, May 04 2010

One more term (8783) added (unknown discoverer) corresponding to a probable prime with 6834 digits by Jean-Louis Charton, Oct 06 2010

Status

approved