OFFSET
0,5
COMMENTS
Essentially the same as A077980.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1, -2, 2).
FORMULA
From Reinhard Zumkeller, Oct 07 2008: (Start)
a(n+1) = a(n) - 2*a(n-1) + 2*a(n-2).
a(n) = A077925(floor(n/2)-1) for n>1. (End)
MAPLE
seq(coeff(series(1/(1-x+2*x^2-2*x^3), x, n+1), x, n), n = 0 .. 40); # G. C. Greubel, Aug 07 2019
MATHEMATICA
CoefficientList[Series[1/(1-x+2x^2-2x^3), {x, 0, 50}], x] (* or *) LinearRecurrence[{1, -2, 2}, {1, 1, -1}, 50] (* Harvey P. Dale, Aug 27 2014 *)
PROG
(PARI) Vec(1/(1-x+2*x^2-2*x^3)+O(x^50)) \\ Charles R Greathouse IV, Sep 25 2012
(Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( 1/(1-x+2*x^2-2*x^3) )); // G. C. Greubel, Aug 07 2019
(Sage) (1/(1-x+2*x^2-2*x^3)).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Aug 07 2019
(GAP) a:=[1, 1, -1];; for n in [4..50] do a[n]:=a[n-1]-2*a[n-2]+2*a[n-3]; od; a; # G. C. Greubel, Aug 07 2019
CROSSREFS
KEYWORD
sign,easy
AUTHOR
N. J. A. Sloane, Nov 17 2002, Jun 17 2007
STATUS
approved