A121365 a(n) = 6*a(n-1) - 9*a(n-2) + n + 1.

1, 1, 1, 2, 9, 43, 185, 732, 2737, 9845, 34449, 118102, 398585, 1328607, 4384393, 14348912, 46633953, 150663529, 484275617, 1549681962, 4939611241, 15690529811, 49686677721, 156905298052, 494251688849

Offset

1,4

Links

Table of n, a(n) for n=1..25.

Index entries for linear recurrences with constant coefficients, signature (8, -22, 24, -9).

Formula

a(n) = (36 + (n-4)*3^n + 9*n)/36.

O.g.f.: -x*(-1+7*x-15*x^2+8*x^3)/((-1+x)^2*(3*x-1)^2). - R. J. Mathar, Dec 10 2007

Maple

A121365:= n-> (36 + (n-4)*3^n + 9*n)/36: seq(A121365(n), n=1..30); # Wesley Ivan Hurt, Apr 29 2014

Mathematica

Table[(9*(n+4)+(n-4)*3^n)/36, {n, 25}]

Crossrefs

Cf. A121968.

Sequence in context: A351882 A132847 A275620 * A018960 A217666 A002310

Adjacent sequences: A121362 A121363 A121364 * A121366 A121367 A121368

Keyword

nonn,easy

Author

Zak Seidov, Sep 06 2006

Status

approved