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 A128338 Numbers k such that (8^k + 5^k)/13 is prime. 17
 7, 19, 167, 173, 223, 281, 21647 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are primes. a(8) > 10^5. - Robert Price, Jan 21 2013 LINKS MATHEMATICA k=8; Do[p=Prime[n]; f=(k^p+5^p)/(k+5); If[ PrimeQ[f], Print[p] ], {n, 1, 100}] PROG (PARI) is(n)=isprime((8^n+5^n)/13) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A057171, A082387, A122853, A128335, A128336, A128337, 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: A267276 A096321 A201806 * A173384 A107195 A201479 Adjacent sequences:  A128335 A128336 A128337 * A128339 A128340 A128341 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Feb 27 2007 EXTENSIONS a(7) from Robert Price, Jan 21 2013 STATUS approved

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Last modified May 25 15:44 EDT 2019. Contains 323572 sequences. (Running on oeis4.)