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 A257790 Numbers n such that 6*5^n - 1 is prime. 1
 0, 1, 2, 5, 11, 28, 65, 72, 361, 479, 494, 599, 1062, 1094, 1193, 2827, 3271, 3388, 3990, 4418, 11178, 16294, 25176, 42500, 68320, 85698, 145259, 159119, 169771 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS All terms correspond to verified primes, that is, not merely probable primes. a(30) > 2*10^5. LINKS MATHEMATICA Select[Range[0, 10000], PrimeQ[6*5^# - 1] &] PROG (MAGMA) [n: n in [0..2*10^3] | IsPrime(6*5^n-1)]; // Vincenzo Librandi, May 09 2015 (PARI) is(n)=ispseudoprime(6*5^n-1) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A143279. Sequence in context: A027087 A055227 A325916 * A174145 A124016 A121398 Adjacent sequences:  A257787 A257788 A257789 * A257791 A257792 A257793 KEYWORD nonn,hard,more AUTHOR Robert Price, May 08 2015 STATUS approved

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Last modified February 24 06:13 EST 2020. Contains 332199 sequences. (Running on oeis4.)