

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
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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



