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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 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 January 21 10:26 EST 2020. Contains 331105 sequences. (Running on oeis4.)