A091103 Expansion of (1-3x+12x^2)/((1-3x)(1+3x)).

1, -3, 21, -27, 189, -243, 1701, -2187, 15309, -19683, 137781, -177147, 1240029, -1594323, 11160261, -14348907, 100442349, -129140163, 903981141, -1162261467, 8135830269, -10460353203, 73222472421, -94143178827, 659002251789, -847288609443

Offset

0,2

Comments

a(0)=1, a(2n-1)=-k^(2n-1), a(2n)=(3k-2)k^(2n-1), k=3; G.f.: (1-kx+2(k-1)kx^2)/((1-kx)(1+kx)), k=3.

Links

Table of n, a(n) for n=0..25.

Index entries for linear recurrences with constant coefficients, signature (0,9).

Formula

a(n)=2*3^n/3+5(-3)^n/3-4*0^n/3

Crossrefs

Sequence in context: A074217 A350247 A062219 * A363409 A292310 A045802

Adjacent sequences: A091100 A091101 A091102 * A091104 A091105 A091106

Keyword

easy,sign

Author

Paul Barry, Dec 22 2003

Status

approved