OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (-2,1,-2).
FORMULA
a(n) = -2*a(n-1)+a(n-2)-2*a(n-3) with a(0)=1, a(1)=-2, a(2)=5. - Harvey P. Dale, Dec 27 2013
a(n) = (-1)^n * A077938(n). - G. C. Greubel, Jun 25 2019
MATHEMATICA
CoefficientList[Series[1/(1+2x-x^2+2x^3), {x, 0, 40}], x] (* or *) LinearRecurrence[{-2, 1, -2}, {1, -2, 5}, 40] (* Harvey P. Dale, Dec 27 2013 *)
PROG
(PARI) Vec(1/(1+2*x-x^2+2*x^3)+O(x^40)) \\ Charles R Greathouse IV, Sep 27 2012
(Magma) R<x>:=PowerSeriesRing(Integers(), 40); Coefficients(R!( 1/(1+2*x-x^2+2*x^3) )); // G. C. Greubel, Jun 25 2019
(Sage) (1/(1+2*x-x^2+2*x^3)).series(x, 40).coefficients(x, sparse=False) # G. C. Greubel, Jun 25 2019
(GAP) a:=[1, -2, 5];; for n in [4..40] do a[n]:=-2*a[n-1]+a[n-2]-2*a[n-3]; od; a; # G. C. Greubel, Jun 25 2019
CROSSREFS
KEYWORD
sign,easy
AUTHOR
N. J. A. Sloane, Nov 17 2002
STATUS
approved