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 A291983 #13 Jun 12 2022 11:09:40
%S A291983 1,-1,0,-1,2,-1,1,-2,2,-2,2,-2,3,-3,2,-3,4,-3,3,-4,4,-4,4,-4,5,-5,4,
%T A291983 -5,6,-5,5,-6,6,-6,6,-6,7,-7,6,-7,8,-7,7,-8,8,-8,8,-8,9,-9,8,-9,10,-9,
%U A291983 9,-10,10,-10,10,-10,11,-11,10,-11,12,-11,11,-12,12,-12,12
%N A291983 Expansion of 1/((1+x)*(1+x^2)*(1+x^3)).
%H A291983 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (-1, -1, -2, -1, -1, -1).
%t A291983 CoefficientList[Series[1/((1+x)(1+x^2)(1+x^3)),{x,0,70}],x] (* or *) LinearRecurrence[ {-1,-1,-2,-1,-1,-1},{1,-1,0,-1,2,-1},80] (* _Harvey P. Dale_, Jun 12 2022 *)
%o A291983 (PARI) Vec(1/((1+x)*(1+x^2)*(1+x^3)) + O(x^100))
%Y A291983 Cf. A112689, A291954, A291984, A291985.
%K A291983 sign
%O A291983 0,5
%A A291983 _Seiichi Manyama_, Sep 07 2017