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A128348 Numbers k such that (12^k - 5^k)/7 is prime. 20
2, 3, 31, 41, 53, 101, 421, 1259, 4721, 45259 (list; graph; refs; listen; history; text; internal format)
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
Sequence in context: A136150 A155056 A110456 * A029973 A344736 A347332
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Feb 27 2007
EXTENSIONS
a(8) and a(9) from Ray G. Opao, Jul 01 2012
a(10) from Robert Price, Mar 02 2013
STATUS
approved

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Last modified March 28 08:22 EDT 2024. Contains 371236 sequences. (Running on oeis4.)