A032124 "BIK" (reversible, indistinct, unlabeled) transform of 2,2,2,2...

2, 5, 12, 33, 90, 261, 756, 2241, 6642, 19845, 59292, 177633, 532170, 1595781, 4785156, 14353281, 43053282, 129153285, 387440172, 1162300833, 3486843450, 10460471301, 31381236756, 94143533121, 282430067922, 847289672325, 2541867422652, 7625600673633

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

C. G. Bower, Transforms (2)

Index entries for linear recurrences with constant coefficients, signature (3,3,-9).

Formula

a(n) = (1/6)*((5-(-1)^n)*3^floor(n/2) + 2*3^n). - Ralf Stephan, May 11 2004

a(n) = 3*a(n-1)+3*a(n-2)-9*a(n-3). G.f.: -x*(9*x^2+x-2) / ((3*x-1)*(3*x^2-1)). - Colin Barker, Dec 15 2012

Mathematica

CoefficientList[Series[-(9 x^2 + x - 2)/((3 x - 1) (3 x^2 - 1)), {x, 0, 30}], x] (* Vincenzo Librandi, Oct 19 2013 *)

Prog

(Magma) [(1/6)*((5-(-1)^n)*3^Floor(n/2) + 2*3^n): n in [1..30]]; // Vincenzo Librandi, Oct 19 2013

Crossrefs

Sequence in context: A292212 A212823 A292213 * A292214 A292215 A292216

Adjacent sequences: A032121 A032122 A032123 * A032125 A032126 A032127

Keyword

nonn,easy

Author

Christian G. Bower

Extensions

More terms from Vincenzo Librandi, Oct 19 2013

Status

approved