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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

Table of n, a(n) for n=0..39.

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 June 17 04:26 EDT 2019. Contains 324183 sequences. (Running on oeis4.)