A133672 a(n) = a(n-1) - 81*a(n-2), a(0)=1, a(1)=9.

1, 9, -72, -801, 5031, 69912, -337599, -6000471, 21345048, 507383199, -1221565689, -42319604808, 56627216001, 3484515205449, -1102289290632, -283348020932001, -194062588390809, 22757127107101272, 38476196766756801, -1804851098908446231

Offset: 0

Author

Philippe Deléham, Dec 29 2007

Keywords

• easy
• sign

Links

• Index entries for linear recurrences with constant coefficients, signature (1,-81).

Programs

Mathematica

LinearRecurrence[{1,-81},{1,9},30] (* Harvey P. Dale, Aug 01 2016 *)

Formula

G.f.: (1+8*x)/(1-x+81*x^2).

a(n) = Sum_{k=0..n} A133607(n,k)*9^k. - Philippe Deléham, Dec 30 2007