A077886 Expansion of (1-x)^(-1)/(1+2*x^3).

1, 1, 1, -1, -1, -1, 3, 3, 3, -5, -5, -5, 11, 11, 11, -21, -21, -21, 43, 43, 43, -85, -85, -85, 171, 171, 171, -341, -341, -341, 683, 683, 683, -1365, -1365, -1365, 2731, 2731, 2731, -5461, -5461, -5461, 10923, 10923, 10923, -21845, -21845, -21845, 43691, 43691, 43691, -87381, -87381, -87381, 174763

Offset: 0

Author

N. J. A. Sloane, Nov 17 2002

Keywords

• sign
• easy

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..1000
• Index entries for linear recurrences with constant coefficients, signature (1,0,-2,2).

Programs

Mathematica

CoefficientList[Series[(1-x)^(-1)/(1+2x^3),{x,0,60}],x] (* or *) LinearRecurrence[{1,0,-2,2},{1,1,1,-1},60] (* Harvey P. Dale, Apr 30 2016 *)

PARI

a(n)=([0,1,0,0; 0,0,1,0; 0,0,0,1; 2,-2,0,1]^n*[1;1;1;-1])[1,1] \\ Charles R Greathouse IV, Oct 03 2016

Formula

a(0)=1, a(1)=1, a(2)=1, a(3)=-1, a(n)=a(n-1)-2*a(n-3)+2*a (n-4). - Harvey P. Dale, Apr 30 2016