OFFSET
0,4
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (-1,-2,-1).
FORMULA
G.f.: 1 - x/(G(0) + x) where G(k)= 1 - x*(k+1)/(1 - 1/(1 + (k+1)/G(k+1)));(continued fraction, 3-step). - Sergei N. Gladkovskii, Nov 17 2012
a(n) = (-1)^n*A077954(n). - R. J. Mathar, Jul 10 2013
MATHEMATICA
CoefficientList[Series[1/(1+x+2x^2+x^3), {x, 0, 50}], x] (* or *) LinearRecurrence[ {-1, -2, -1}, {1, -1, -1}, 50] (* Harvey P. Dale, Apr 18 2016 *)
PROG
(PARI) my(x='x+O('x^50)); Vec(1/(1+x+2*x^2+x^3)) \\ G. C. Greubel, Jun 25 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( 1/(1+x+2*x^2+x^3) )); // G. C. Greubel, Jun 25 2019
(Sage) (1/(1+x+2*x^2+x^3)).series(x, 50).coefficients(x, sparse=False) # G. C. Greubel, Jun 25 2019
(GAP) a:=[1, -1, -1];; for n in [4..50] do a[n]:=-a[n-1]-2*a[n-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