A128338 Numbers k such that (8^k + 5^k)/13 is prime.

7, 19, 167, 173, 223, 281, 21647

Offset

1,1

Comments

All terms are primes.

a(8) > 10^5. - Robert Price, Jan 21 2013

Links

Table of n, a(n) for n=1..7.

Mathematica

k=8; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

Prog

(PARI) is(n)=isprime((8^n+5^n)/13) \\ Charles R Greathouse IV, Feb 17 2017

Crossrefs

Cf. A057171, A082387, A122853, A128335, A128336, A128337, A128339, 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: A096321 A201806 A346943 * A173384 A107195 A201479

Adjacent sequences: A128335 A128336 A128337 * A128339 A128340 A128341

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 27 2007

Extensions

a(7) from Robert Price, Jan 21 2013

Status

approved