A218373 Numbers n such that (7^n + 4^n)/11 is prime.

3, 5, 19, 41, 47, 8231, 33931, 43781, 50833, 53719, 67211

Offset

1,1

Comments

All terms are primes.

a(11) > 10^5

Links

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

Mathematica

Do[ p=Prime[n]; f=(7^p+4^p)/11; If[ PrimeQ[f], Print[p]], {n, 1, 9592} ]

Prog

(PARI) is(n)=ispseudoprime((7^n+4^n)/11) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A128335, A128067, A128337.

Sequence in context: A148532 A148533 A242818 * A034511 A133603 A201867

Adjacent sequences: A218370 A218371 A218372 * A218374 A218375 A218376

Keyword

hard,more,nonn

Author

Robert Price, Oct 27 2012

Status

approved