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

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

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.

a(0)=1, a(2n-1)=-k^(2n-1), a(2n)=(3k-2)*k^(2n-1), where k=3.

G.f.: (1-k*x+2*(k-1)*k*x^2)/((1-k*x)*(1+k*x)), where k=3.

Crossrefs

Sequence in context: A074217 A350247 A062219 * A363409 A292310 A045802

Adjacent sequences: A091100 A091101 A091102 * A091104 A091105 A091106

Keyword

easy,sign,changed

Author

Paul Barry, Dec 22 2003

Status

approved