A128347 Numbers k such that (11^k - 5^k)/6 is prime.

5, 41, 149, 229, 263, 739, 3457, 20269, 98221

Offset

1,1

Comments

All terms are primes.

a(10) > 10^5. - Robert Price, Jan 24 2013

Links

Table of n, a(n) for n=1..9.

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)/6) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A062572, A128344, A128345, A128346, A128348, A128349, A128350, A128351, A128352, A128353, A128354. Cf. A004061, A082182, A121877, A059802. Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128338, A128339, A128340, A128341, A128342.

Sequence in context: A102265 A337393 A262340 * A349336 A056905 A105412

Adjacent sequences: A128344 A128345 A128346 * A128348 A128349 A128350

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 27 2007

Extensions

a(7)-a(9) from Robert Price, Jan 24 2013

Status

approved