A136427 a(n) = 3*a(n-1)-4*a(n-2)+6*a(n-3)-4*a(n-4).

0, 1, 2, 4, 10, 24, 48, 92, 188, 388, 772, 1524, 3060, 6164, 12308, 24532, 49108, 98388, 196692, 393044, 786260, 1573204, 3146068, 6290772, 12582228, 25167188, 50333012, 100660564, 201323860, 402658644, 805311828, 1610601812, 3221214548

Offset

0,3

Links

Table of n, a(n) for n=0..32.

Index entries for linear recurrences with constant coefficients, signature (3,-4,6,-4).

Formula

From R. J. Mathar, Apr 25 2008: (Start)

G.f.: x*(1-x+2*x^2+2*x^4)/((x-1)*(2*x-1)*(2*x^2+1)).

a(n) = 3*2^(n-2)-(-1)^[(n+1)/2]*A016116(n+1)/6-4/3, n > 1. (End)

a(n) = -(2/3)+(2/3)*2^n-[(1/12)*I]*[I*sqrt(2)]^n*sqrt(2)+[(1/12)*I]*sqrt(2)*[ -I*sqrt(2)]^n, with n>=0 and I=sqrt(-1). - Paolo P. Lava, Jun 09 2008

Crossrefs

Sequence in context: A009884 A032023 A094837 * A350881 A018114 A356695

Adjacent sequences: A136424 A136425 A136426 * A136428 A136429 A136430

Keyword

nonn,easy

Author

Paul Curtz, Apr 01 2008

Status

approved