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 A129688 #12 Feb 20 2022 01:26:57
%S A129688 1,0,1,2,0,1,0,2,0,1,2,0,2,0,1,0,2,0,2,0,1,2,0,2,0,2,0,1,0,2,0,2,0,2,
%T A129688 0,1,2,0,2,0,2,0,2,0,1,0,2,0,2,0,2,0,2,0,1
%N A129688 A129686 * A128174.
%C A129688 Resulting triangle has (1, 0, 2, 0, 2, 0, 2, ...) in every column.
%C A129688 Row sums = A109613: (1, 1, 3, 3, 5, 5, ...).
%F A129688 A129686 * A128174 as infinite lower triangular matrices.
%e A129688 First few rows of the triangle:
%e A129688 1;
%e A129688 0, 1;
%e A129688 2, 0, 1;
%e A129688 0, 2, 0, 1;
%e A129688 2, 0, 2, 0, 1;
%e A129688 ...
%t A129688 T[n_, k_] := If[k == n, 1, If[EvenQ[n + k], 2, 0]];
%t A129688 Table[T[n, k], {n, 1, 10}, {k, 1, n}] // Flatten (* _Jean-François Alcover_, Jul 10 2019 *)
%Y A129688 Cf. A129686, A128174, A109613.
%K A129688 nonn,tabl
%O A129688 1,4
%A A129688 _Gary W. Adamson_, Apr 28 2007