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 A128003 Numbers n such that (37^n - 1)/36 is prime. 9
 13, 71, 181, 251, 463, 521, 7321, 36473, 48157, 87421, 168527 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 7321 is a term found by Richard Fischer in 2004. - Alexander Adamchuk, Feb 11 2007 No other terms less than 100000. - Robert Price, Mar 18 2012 LINKS H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930. H. Lifchitz, Mersenne and Fermat primes field Index to primes in various ranges, form ((k+1)^n-1)/k MATHEMATICA Select[Prime[Range[100]], PrimeQ[(37^#-1)/36]&] PROG (PARI) is(n)=ispseudoprime((37^n-1)/36) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Sequence in context: A067382 A253776 A158941 * A060103 A141989 A159512 Adjacent sequences:  A128000 A128001 A128002 * A128004 A128005 A128006 KEYWORD hard,more,nonn AUTHOR Alexander Adamchuk, Feb 11 2007 EXTENSIONS 7321 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008 a(8)-a(10) from Robert Price, Mar 18 2012 a(11) corresponds to a probable prime discovered by Paul Bourdelais, Aug 05 2019 STATUS approved

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