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 A158020 #17 Nov 17 2019 01:45:53
%S A158020 1,1,-1,-1,0,1,-1,1,1,-1,1,0,-2,0,1,1,-1,-2,2,1,-1,-1,0,3,0,-3,0,1,-1,
%T A158020 1,3,-3,-3,3,1,-1,1,0,-4,0,6,0,-4,0,1,1,-1,-4,4,6,-6,-4,4,1,-1,-1,0,5,
%U A158020 0,-10,0,10,0,-5,0,1,-1,1,5,-5,-10,10,10,-10,-5,5,1,-1
%N A158020 Triangle of coefficients in expansion of (-1-x)^floor(n/2)(1-x)^ceiling(n/2).
%C A158020 Triangle T(n,k), 0 <= k <= n, read by rows given by [1,-2,1,0,0,0,0,0,0,...] DELTA [-1,0,1,0,0,0,0,0,0,...] where DELTA is the operator defined in A084938.
%F A158020 T(n,k) = T(n-2,k-2) - T(n-2,k), T(0,0)=T(1,0)=1, T(1,1)=-1.
%F A158020 G.f.: (1+(1-y)*x)/(1+(1-y^2)*x^2). - _Philippe Deléham_, Dec 02 2011
%e A158020 Triangle begins:
%e A158020 1;
%e A158020 1, -1;
%e A158020 -1, 0, 1;
%e A158020 -1, 1, 1, -1;
%e A158020 1, 0, -2, 0, 1; ...
%t A158020 Flatten[Table[CoefficientList[(-1 - x)^Floor[n/2] (1 - x)^Ceiling[n/2], x], {n, 0, 11}]] (* _T. D. Noe_, Dec 01 2011 *)
%Y A158020 Cf. A051160.
%K A158020 sign,tabl
%O A158020 0,13
%A A158020 _Philippe Deléham_, Mar 11 2009
%E A158020 Corrected by _Philippe Deléham_, Dec 02 2011