A232806 a(n) = a(n-1)^2/2 + 5/2, a(0) = 1.

1, 3, 7, 27, 367, 67347, 2267809207, 2571479299676984427, 3306252894333617140505030630200259167, 5465654100644710254338412340877627345031115357273557843293337076983766947

Offset

0,2

Comments

First differences are 2*A063573.

Links

Andrew Howroyd, Table of n, a(n) for n = 0..12

Formula

a(n) = 2*A002065(n) + 1.

a(n) = 2*A166105(n) - 1. - Robert FERREOL, May 31 2020

a(n) = A002065(n) + A166105(n). - Alois P. Heinz, Jun 07 2020

Mathematica

NestList[(5 + #^2)/2 &, 1, 10] (* Paolo Xausa, Oct 31 2025 *)

Prog

(PARI) a(n) = my(x=1); for(n=1, n, x = (x^2 + 5)/2); x \\ Andrew Howroyd, Oct 30 2025

Crossrefs

Cf. A063573, A002065, A166105.

Sequence in context: A267625 A161370 A280020 * A270349 A281701 A393927

Adjacent sequences: A232803 A232804 A232805 * A232807 A232808 A232809

Keyword

nonn

Author

Richard R. Forberg, Nov 30 2013

Extensions

a(9) added by Andrew Howroyd, Oct 30 2025

Status

approved