A139800 a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4).

1, 0, 0, 0, 2, 2, 4, 8, 18, 34, 68, 136, 274, 546, 1092, 2184, 4370, 8738, 17476, 34952, 69906, 139810, 279620, 559240, 1118482, 2236962, 4473924, 8947848, 17895698, 35791394, 71582788, 143165576, 286331154, 572662306, 1145324612, 2290649224

Offset

0,5

Links

Table of n, a(n) for n=0..35.

Index entries for linear recurrences with constant coefficients, signature (1,1,1,2).

Formula

O.g.f: (-1+x+x^2+x^3)/((2*x-1)(1+x)(1+x^2)). a(n)=2^n/15+(-1)^n/3+A112030(n)/5. - R. J. Mathar, Jun 12 2008

Crossrefs

Sequence in context: A063402 A175195 A369289 * A168058 A007971 A126068

Adjacent sequences: A139797 A139798 A139799 * A139801 A139802 A139803

Keyword

nonn

Author

Paul Curtz, May 22 2008

Extensions

More terms from R. J. Mathar, Jun 12 2008

Status

approved