A128348 - OEIS

A128348

Numbers k such that (12^k - 5^k)/7 is prime.

2, 3, 31, 41, 53, 101, 421, 1259, 4721, 45259

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OFFSET

1,1

COMMENTS

All terms are primes.

Primality of the primes formed by a(8) and a(9) were certified by Primo. - Ray G. Opao, Jul 01 2012

a(11) > 10^5. - Robert Price, Mar 02 2013

LINKS

MATHEMATICA

k=12; Do[p=Prime[n]; f=(k^p-5^p)/(k-5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}]

PROG

(PARI) is(n)=isprime((12^n-5^n)/7) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

KEYWORD

hard,more,nonn

AUTHOR

EXTENSIONS

a(8) and a(9) from Ray G. Opao, Jul 01 2012

a(10) from Robert Price, Mar 02 2013

STATUS

approved