A260982 a(n) = (2^(2^(n+1)) + 2^(2^n) + 1)/21.

1, 13, 3133, 204525373, 878416384666881853, 16203922234330403022943873881213226813, 5513909011300771210646237381366090850171917477741023928710521838825947516733

Offset

1,2

Links

Table of n, a(n) for n=1..7.

Formula

a(n) = A001576(2^n)/21. - Michel Marcus, Aug 14 2015

Example

a(2) = (2^(2^(2+1)) + 2^(2^2) + 1)/21 = 13.

Mathematica

Table[(2^(2^(n + 1)) + 2^(2^n) + 1)/21, {n, 1, 10}] (* Vincenzo Librandi, Aug 08 2015 *)

Prog

(PARI) first(m)=my(v=vector(m, t, (2^(2^(t+1))+2^(2^t)+1)/21)); v; /* Anders Hellström, Aug 07 2015 */
(Magma) [(2^(2^(n+1)) + 2^(2^n) + 1)/21: n in [1..10]]; // Vincenzo Librandi, Aug 08 2015

Crossrefs

Cf. A001576 (1^n + 2^n + 4^n).

Sequence in context: A208315 A296174 A220642 * A159357 A221885 A134159

Adjacent sequences: A260979 A260980 A260981 * A260983 A260984 A260985

Keyword

nonn,easy

Author

Marco Ripà, Aug 07 2015

Status

approved