A107036 Indices of prime Jacobsthal numbers.

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, 986191, 4031399

Offset

1,1

Comments

All terms are prime except a(1) = 4. All prime terms are listed in A000978. - Alexander Adamchuk, Oct 03 2006

Links

Table of n, a(n) for n=1..42.

Formula

a(n) = A000978(n-1) for n >= 3. - 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: A081735 A373142 A227231 * A001605 A216570 A101762

Adjacent sequences: A107033 A107034 A107035 * A107037 A107038 A107039

Keyword

nonn,more

Author

Paul Barry, May 09 2005

Extensions

More terms from Alexander Adamchuk, Oct 03 2006

a(41)-a(42) from Bill McEachen, Aug 28 2024

Status

approved