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 A078016 #14 Sep 08 2022 08:45:08
%S A078016 1,0,-1,-2,-1,2,5,4,-3,-12,-13,2,27,38,9,-56,-103,-56,103,262,215,
%T A078016 -150,-627,-692,85,1404,2011,522,-2893,-5426,-3055,5264,13745,11536,
%U A078016 -7473,-32754,-36817,3410,72981,106388,29997,-149372,-285757,-166382,268747,720886,618521,-371112,-1710519
%N A078016 Expansion of (1-x)/(1-x+x^2+x^3).
%H A078016 G. C. Greubel, <a href="/A078016/b078016.txt">Table of n, a(n) for n = 0..1000</a>
%H A078016 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1, -1, -1).
%F A078016 G.f.: (1-x)/(1-x+x^2+x^3).
%F A078016 a(0)=1, a(1)=0, a(2)=-1, a(n) = a(n-1) - a(n-2) - a(n-3). - _Harvey P. Dale_, Nov 08 2011
%t A078016 CoefficientList[Series[(1-x)/(1-x+x^2+x^3),{x,0,50}],x] (* or *) LinearRecurrence[ {1,-1,-1},{1,0,-1},50] (* _Harvey P. Dale_, Nov 08 2011 *)
%o A078016 (PARI) my(x='x+O('x^50)); Vec((1-x)/(1-x+x^2+x^3)) \\ _G. C. Greubel_, Jun 29 2019
%o A078016 (Magma) R<x>:=PowerSeriesRing(Integers(), 50); Coefficients(R!( (1-x)/(1-x+x^2+x^3) )); // _G. C. Greubel_, Jun 29 2019
%o A078016 (Sage) ((1-x)/(1-x+x^2+x^3)).series(x, 50).coefficients(x, sparse=False) # _G. C. Greubel_, Jun 29 2019
%o A078016 (GAP) a:=[1,0,-1];; for n in [4..50] do a[n]:=a[n-1]-a[n-2]-a[n-3]; od; a; # _G. C. Greubel_, Jun 29 2019
%K A078016 sign
%O A078016 0,4
%A A078016 _N. J. A. Sloane_, Nov 17 2002