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 A071382 Numbers n such that (30^n+1)/31 is a prime. 15
 139, 173, 547, 829, 2087, 2719, 3109, 10159, 56543, 80599 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Some of the larger terms may only correspond to probable primes. a(11) > 10^5. - Robert Price, Jul 10 2013 LINKS H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7. H. Lifchitz, Mersenne and Fermat primes field MATHEMATICA Select[Range[3000], PrimeQ[(30^# + 1) / 31] &] (* Vincenzo Librandi, Oct 29 2017 *) PROG (PARI) isok(n) = (denominator(p=(30^n+1)/31)==1) && isprime(p); \\ Michel Marcus, Oct 29 2017 CROSSREFS Cf. A071381. Sequence in context: A325075 A020357 A050967 * A290450 A209618 A031928 Adjacent sequences:  A071379 A071380 A071381 * A071383 A071384 A071385 KEYWORD nonn,more AUTHOR Rick L. Shepherd, May 22 2002 EXTENSIONS a(8) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008 a(9)-a(10) from Robert Price, Jul 10 2013 STATUS approved

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Last modified December 10 23:29 EST 2019. Contains 329910 sequences. (Running on oeis4.)