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 A107036 Indices of prime Jacobsthal numbers. 13
 3, 4, 5, 7, 11, 13, 17, 19, 23, 31, 43, 61, 79, 101, 127, 167, 191, 199, 313, 347, 701, 1709, 2617, 3539, 5807, 10501, 10691, 11279, 12391, 14479, 42737, 83339, 95369, 117239, 127031, 138937, 141079, 267017, 269987, 374321 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS All a(n) are prime except a(1) = 4. All prime a(n) are listed in A000978[n] = {3,5,7,11,13,17,19,23,31,43,61,79,101,127,167,...} Numbers n such that (2^n + 1)/3 is prime. - Alexander Adamchuk, Oct 03 2006 LINKS FORMULA a(n) = A000978(n) for n>1. - Alexander Adamchuk, Oct 03 2006 PROG (PARI) is(n)=ispseudoprime((2^n - (-1)^n) / 3) \\ Charles R Greathouse IV, Apr 28 2015 CROSSREFS Cf. A000978, A001045, A001605. Sequence in context: A140826 A081735 A227231 * A001605 A216570 A101762 Adjacent sequences:  A107033 A107034 A107035 * A107037 A107038 A107039 KEYWORD nonn AUTHOR Paul Barry, May 09 2005 EXTENSIONS More terms from Alexander Adamchuk, Oct 03 2006 STATUS approved

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Last modified October 17 16:51 EDT 2019. Contains 328120 sequences. (Running on oeis4.)