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 A131227 #4 Feb 26 2022 00:34:13
%S A131227 1,2,3,1,2,5,2,1,2,7,1,2,1,2,9,2,1,2,1,2,11,1,2,1,2,1,2,13,2,1,2,1,2,
%T A131227 1,2,15,1,2,1,2,1,2,1,2,17,2,1,2,1,2,1,2,1,2,19
%N A131227 2*A051340 - A128174.
%C A131227 Row sums = A047383, numbers congruent to {1,5} mod 7: (1, 5, 8, 12, 15, 19, ...)
%F A131227 2*A051340 - A128174 as infinite lower triangular matrices.
%e A131227 First few rows of the triangle:
%e A131227 1;
%e A131227 2, 3;
%e A131227 1, 2, 5;
%e A131227 2, 1, 2, 7;
%e A131227 1, 2, 1, 2, 9;
%e A131227 2, 1, 2, 1, 2, 11;
%e A131227 1, 2, 1, 2, 1, 2, 13;
%e A131227 ...
%Y A131227 Cf. A051340, A128174, A047383, A131228, A131229.
%K A131227 nonn,tabl
%O A131227 0,2
%A A131227 _Gary W. Adamson_, Jun 20 2007