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 A128337 Numbers k such that (7^k + 5^k)/12 is prime. 19
 11, 31, 173, 271, 547, 1823, 2111, 5519, 7793, 22963, 41077, 49739 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are primes. a(13) > 10^5. - Robert Price, Nov 20 2012 LINKS MATHEMATICA k=7; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}] PROG (PARI) is(n)=isprime((7^n+5^n)/12) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A057171, A082387, A122853, A128335, A128336, A128338, A128339, A128340, A128341, A128342, A128343. Cf. A004061, A082182, A121877, A059802. Cf. A062572, A128344, A128345, A128346, A128347, A128348, A128349, A128350, A128351, A128352, A128353, A128354. Sequence in context: A001604 A144727 A002535 * A093382 A098264 A023279 Adjacent sequences:  A128334 A128335 A128336 * A128338 A128339 A128340 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Feb 27 2007 EXTENSIONS a(6)-a(12) from Robert Price, Nov 20 2012 STATUS approved

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Last modified July 24 14:51 EDT 2021. Contains 346273 sequences. (Running on oeis4.)