A128340 Numbers k such that (11^k + 5^k)/16 is prime.

7, 11, 181, 421, 2297, 2797, 4129, 4139, 7151, 29033

Offset

1,1

Comments

All terms are primes.

a(11) > 10^5. - Robert Price, Feb 09 2013

Links

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

Mathematica

k=11; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

Prog

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

Crossrefs

Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128338, A128339, A128341, A128342, A128343.

Cf. A004061, A082182, A121877, A059802.

Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128351, A128352, A128353, A128354.

Sequence in context: A038543 A145953 A154303 * A106716 A292791 A106818

Adjacent sequences: A128337 A128338 A128339 * A128341 A128342 A128343

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 27 2007

Extensions

a(5)-a(10) from Robert Price, Feb 09 2013

Status

approved