A077931 Expansion of 1/((1-x)*(1+2*x+x^2+2*x^3)).

1, -1, 2, -4, 9, -17, 34, -68, 137, -273, 546, -1092, 2185, -4369, 8738, -17476, 34953, -69905, 139810, -279620, 559241, -1118481, 2236962, -4473924, 8947849, -17895697, 35791394, -71582788, 143165577, -286331153, 572662306, -1145324612, 2290649225, -4581298449, 9162596898

Offset: 0

Author

N. J. A. Sloane, Nov 17 2002

Keywords

• sign
• easy

Links

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

Programs

Mathematica

CoefficientList[Series[1/((1 - x) * (1 + 2 x + x^2 + 2 x^3)), {x, 0, 50}], x] (* Vladimir Joseph Stephan Orlovsky, Jun 20 2011 *)

PARI

Vec(1/((1-x)*(1+2*x+x^2+2*x^3))+O(x^99)) \\ Charles R Greathouse IV, Sep 27 2012