A275575 Numbers k such that (3^k + 1)/(3 - (-1)^k) is a prime.

2, 3, 4, 5, 7, 13, 16, 23, 32, 43, 64, 281, 359, 487, 577, 1579, 1663, 1741, 3191, 9209, 11257, 12743, 13093, 17027, 26633, 104243, 134227, 152287, 700897, 1205459

Offset

1,1

Links

Table of n, a(n) for n=1..30.

Maple

A275575:=n->`if`(isprime((3^n + 1)/(3 - (-1)^n)), n, NULL): seq(A275575(n), n=1..2*10^3); # Wesley Ivan Hurt, Dec 26 2016

Mathematica

Select[Range[0, 10^3], PrimeQ[(3^# + 1)/(3 - (-1)^#)] &]

Prog

(PARI) isok(n) = isprime( (3^n + 1)/(3 - (-1)^n)); \\ Michel Marcus, Dec 26 2016

Crossrefs

Cf. A007658, A171381, A280083.

Sequence in context: A100676 A193769 A226790 * A066661 A268199 A178767

Adjacent sequences: A275572 A275573 A275574 * A275576 A275577 A275578

Keyword

nonn,more

Author

Thomas Ordowski, Dec 25 2016

Status

approved