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 A130194 #8 Feb 20 2022 14:43:13
%S A130194 1,2,1,-1,2,1,-4,-1,2,1,1,-4,-1,2,1,6,1,-4,-1,2,1,-1,6,1,-4,-1,2,1,-8,
%T A130194 -1,6,1,-4,-1,2,1,1,-8,-1,6,1,-4,-1,2,1,10,1,-8,-1,6,1,-4,-1,2,1,-1,
%U A130194 10,1,-8,-1,6,1,-4,-1,2,1,-12,-1,10,1,-8,-1,6,1,-4,-1,2,1
%N A130194 Let M = lower triangular matrix with 1's on and below the main diagonal, with columns multiplied by +1, +1, -1, -1, repeated; form M^2; read across rows of resulting triangle.
%C A130194 A000012(signed)^2.
%C A130194 Left border = A009531: (1, 2, -1, -4, 1, 6, -1, ...).
%C A130194 Row sums = A130195: (1, 3, 2, -2, -1, 5, 4, ...).
%C A130194 Row sums of the unsigned triangle = A058074: (1, 3, 4, 8, 9, 15, ...).
%C A130194 A009531 in every column: (1, 2, -1, -4, 1, 6, -1, ...).
%e A130194 First few rows of the triangle:
%e A130194 1;
%e A130194 2, 1;
%e A130194 -1, 2, 1;
%e A130194 -4, -1, 2, 1;
%e A130194 1, -4, -1, 2, 1;
%e A130194 6, 1, -4, -1, 2, 1;
%e A130194 ...
%o A130194 (PARI) trg(nn) = {vgf = x*(1+x)^2/(1+x^2)^2 + O(x^(nn+1)); m = matrix(nn, nn, i, j, if (i >= j, polcoeff(vgf, i-j+1))); for (n=1, nn, for (k=1, n, print1(m[n, k], ", ");); print(););} \\ _Michel Marcus_, Oct 03 2014
%Y A130194 Cf. A000012, A058074, A009531.
%K A130194 tabl,sign
%O A130194 1,2
%A A130194 _Gary W. Adamson_, May 16 2007
%E A130194 More terms from _Michel Marcus_, Oct 03 2014