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
Keywords
Links
- 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
Extensions
More terms from R. J. Mathar, Jun 12 2008