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 A181987 Numbers n such that (39^n - 1)/38 is prime. 1
 349, 631, 4493, 16633, 36341 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Harvey Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930. Henri Lifchitz, Mersenne and Fermat primes field MATHEMATICA Select[Prime[Range[100000]], PrimeQ[(39^#-1)/38]&] PROG (PARI) is(n)=ispseudoprime((39^n-1)/38) \\ Charles R Greathouse IV, Jun 13 2017 CROSSREFS Cf. A028491, A004061, A004062, A004063, A004023, A005808, A004064, A016054, A006032, A006033, A006034, A006035, A127995, A127996, A127997, A127998, A127999, A098438, A128002, A128003, A128004, A128005. Sequence in context: A230609 A177174 A139658 * A054824 A031420 A273530 Adjacent sequences:  A181984 A181985 A181986 * A181988 A181989 A181990 KEYWORD hard,more,nonn AUTHOR Robert Price, Apr 04 2012 STATUS approved

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Last modified December 13 22:55 EST 2019. Contains 329974 sequences. (Running on oeis4.)