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A128348 Numbers n such that (12^n - 5^n)/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

Table of n, a(n) for n=1..10.

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

Cf. A062572, A128344, A128345, A128346, A128347, 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: A136150 A155056 A110456 * A029973 A054551 A049065

Adjacent sequences:  A128345 A128346 A128347 * A128349 A128350 A128351

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 May 19 02:29 EDT 2019. Contains 323377 sequences. (Running on oeis4.)