This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A077911 #12 Sep 08 2022 08:45:07
%S A077911 1,0,-1,3,0,-6,10,3,-28,33,27,-120,100,168,-487,252,891,-1881,352,
%T A077911 4302,-6886,-1365,19440,-23595,-16649,83280,-73576,-109632,340065,
%U A077911 -194376,-595385,1324203,-327808,-2915982,4895802,608355,-13315940,16995033,10245203,-57551208,54055836,71291784
%N A077911 Expansion of 1/((1-x)*(1+x+2*x^2-x^3)).
%H A077911 G. C. Greubel, <a href="/A077911/b077911.txt">Table of n, a(n) for n = 0..1000</a>
%H A077911 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,-1,3,-1).
%t A077911 LinearRecurrence[{0,-1,3,-1}, {1,0,-1,3}, 50] (* or *) CoefficientList[ Series[1/((1-x)*(1+x+2*x^2-x^3)), {x,0,50}], x] (* _G. C. Greubel_, Jul 02 2019 *)
%o A077911 (PARI) Vec(1/((1-x)*(1+x+2*x^2-x^3))+O(x^50)) \\ _Charles R Greathouse IV_, Sep 27 2012
%o A077911 (Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( 1/((1-x)*(1+x+2*x^2-x^3)) )); // _G. C. Greubel_, Jul 02 2019
%o A077911 (Sage) (1/((1-x)*(1+x+2*x^2-x^3))).series(x, 50).coefficients(x, sparse=False) # _G. C. Greubel_, Jul 02 2019
%o A077911 (GAP) a:=[1,0,-1,3];; for n in [4..50] do a[n]:=-a[n-2]+3*a[n-3]-a[n-4]; od; a; # _G. C. Greubel_, Jul 02 2019
%Y A077911 Cf. A077978.
%K A077911 sign,easy
%O A077911 0,4
%A A077911 _N. J. A. Sloane_, Nov 17 2002