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 A128068 Numbers k such that (3^k + 8^k)/11 is prime. 8
 5, 163, 191, 229, 271, 733, 21059, 25237 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are primes. a(9) > 10^5. - Robert Price, Mar 06 2013 LINKS MATHEMATICA k=8; 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+8^n)/11) \\ 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, A128069, A128070, A128071, 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: A301667 A195950 A195951 * A197095 A247468 A304056 Adjacent sequences:  A128065 A128066 A128067 * A128069 A128070 A128071 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Feb 14 2007 EXTENSIONS a(6) from Alexander Adamchuk, Feb 14 2007 a(7)-a(8) from Robert Price, Mar 06 2013 STATUS approved

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Last modified December 12 17:33 EST 2019. Contains 329960 sequences. (Running on oeis4.)