OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..5000
Index entries for linear recurrences with constant coefficients, signature (1,0,1,-1).
FORMULA
G.f.: ( 1+x-x^2+x^3 ) / ( (1+x+x^2)*(x-1)^2 ). - R. J. Mathar, May 23 2014
a(n) = (2/9)*(3*n+3+3*cos(2*(n-1)*Pi/3)-2*sqrt(3)*sin(2*(n-1)*Pi/3)). - Wesley Ivan Hurt, Sep 30 2017
MATHEMATICA
CoefficientList[Series[(1+x-x^2+x^3)/((1+x+x^2)*(x-1)^2), {x, 0, 50}], x] (* G. C. Greubel, Feb 10 2018 *)
LinearRecurrence[{1, 0, 1, -1}, {1, 2, 1, 3}, 74] (* Robert G. Wilson v, Feb 10 2018 *)
PROG
(PARI) my(x='x+O('x^70)); Vec((1+x-x^2+x^3)/((1+x+x^2)*(x-1)^2)) \\ G. C. Greubel, Feb 10 2018
(Magma) Q:=Rationals(); R<x>:=PowerSeriesRing(Q, 70); Coefficients(R!((1+x-x^2+x^3)/((1+x+x^2)*(x-1)^2))) // G. C. Greubel, Feb 10 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Oct 18 2007
STATUS
approved