A099175 a(1) = 1, a(2) = 8; for n > 2: a(n) = a(n-1)*(3*a(n-1)-2).

1, 8, 176, 92576, 25710762176, 1983129874961075240576, 11798412302889389755255045998938726679954176, 417607598606915139792416465578985202696175989567316713156694229302007260054247019608576

Offset: 1

Author

Jonathan Vos Post, Nov 15 2004

Keywords

• nonn

Comments

n*(3n-2) is the n-th octagonal number (A000567).

Crossrefs

Cf. A000567, A003487.

Programs

Mathematica

Join[{1}, NestList[ #*(3*# - 2) &, 8, 7]]

Formula

a(n) = (A003487(n-1)+1)/3 for n >= 2. - Ondrej Kutal, Sep 08 2023

Extensions

Edited by Stefan Steinerberger, Jul 25 2007