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%I #14 Sep 08 2022 08:45:08
%S 1,-2,6,-14,36,-88,220,-544,1352,-3352,8320,-20640,51216,-127072,
%T 315296,-782304,1941056,-4816128,11949760,-29649664,73566592,
%U -182532992,452899840,-1123732480,2788198656,-6918062592,17165057536,-42589842944,105673675776,-262196922368
%N Expansion of 1/(1+2*x-2*x^2-2*x^3).
%H G. C. Greubel, <a href="/A077981/b077981.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-2,2,2).
%F a(n) = (-1)^n * A077937(n). - _Ivan Neretin_, Jun 19 2015
%t LinearRecurrence[{-2,2,2}, {1,-2,6}, 30] (* or *) CoefficientList[ Series[1/(1+2*x-2*x^2-2*x^3), {x,0,30}], x] (* _G. C. Greubel_, Jun 25 2019 *)
%o (PARI) Vec(1/(1+2*x-2*x^2-2*x^3) + O(x^30)) \\ _Michel Marcus_, Jun 19 2015
%o (Magma) R<x>:=PowerSeriesRing(Integers(), 30); Coefficients(R!( 1/(1+2*x-2*x^2-2*x^3) )); // _G. C. Greubel_, Jun 25 2019
%o (Sage) (1/(1+2*x-2*x^2-2*x^3)).series(x, 30).coefficients(x, sparse=False) # _G. C. Greubel_, Jun 25 2019
%o (GAP) a:=[1,-2,6];; for n in [4..30] do a[n]:=-2*a[n-1]+2*a[n-2]+ 2*a[n-3]; od; a; # _G. C. Greubel_, Jun 25 2019
%Y Cf. A077937.
%K sign,easy
%O 0,2
%A _N. J. A. Sloane_, Nov 17 2002