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A133672 a(n) = a(n-1) - 81*a(n-2), a(0)=1, a(1)=9. 1
1, 9, -72, -801, 5031, 69912, -337599, -6000471, 21345048, 507383199, -1221565689, -42319604808, 56627216001, 3484515205449, -1102289290632, -283348020932001, -194062588390809, 22757127107101272, 38476196766756801, -1804851098908446231 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..19.

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

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

a(n) = -(1/38)*i*sqrt(323)*(1/2 + (1/2)*i*sqrt(323))^n + (1/2)*(1/2 - (1/2)*i*sqrt(323))^n + (1/38)*i*sqrt(323)*(1/2 - (1/2)*i*sqrt(323))^n + (1/2)*(1/2 + (1/2)*i*sqrt(323))^n, with n>=0 and i=sqrt(-1). - Paolo P. Lava, Aug 28 2008

MATHEMATICA

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

CROSSREFS

Sequence in context: A006135 A180836 A218126 * A043079 A099973 A091986

Adjacent sequences:  A133669 A133670 A133671 * A133673 A133674 A133675

KEYWORD

easy,sign

AUTHOR

Philippe Deléham, Dec 29 2007

STATUS

approved

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Last modified January 20 02:48 EST 2022. Contains 350467 sequences. (Running on oeis4.)