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 A128071 Numbers k such that (3^k + 13^k)/16 is prime. 12
 3, 7, 127, 2467, 3121, 34313 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are primes. a(4) is certified prime by primo; a(5) is a probable prime. - Ray G. Opao, Aug 02 2007 a(7) > 10^5. - Robert Price, Apr 14 2013 LINKS MATHEMATICA k=13; Do[ p=Prime[n]; f=(3^p+k^p)/(k+3); If[ PrimeQ[f], Print[p]], {n, 1, 100} ] PROG (PARI) is(n)=isprime((3^n+13^n)/16) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A007658 = numbers n such that (3^n + 1)/4 is prime. Cf. A057469 = numbers n such that (3^n + 2^n)/5 is prime. Cf. A122853 = numbers n such that (3^n + 5^n)/8 is prime. Cf. A128066, A128067, A128068, A128069, A128070, A128072, A128073, A128074, A128075. Cf. A059801 = numbers n such that 4^n - 3^n is prime. Cf. A121877 = numbers n such that (5^n - 3^n)/2 is a prime. Cf. A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032. Sequence in context: A042329 A125956 A260642 * A079622 A182330 A005844 Adjacent sequences:  A128068 A128069 A128070 * A128072 A128073 A128074 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Feb 14 2007 EXTENSIONS One more term from Ray G. Opao, Aug 02 2007 a(6) from Robert Price, Apr 14 2013 STATUS approved

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Last modified June 19 06:47 EDT 2019. Contains 324218 sequences. (Running on oeis4.)