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 A143540 #2 Mar 30 2012 17:25:32 %S A143540 0,0,1,0,2,1,0,2,1,0,0,3,2,0,1,0,3,2,0,1,0,0,4,3,0,2,0,1,0,4,3,0,2,0, %T A143540 1,0,0,4,3,0,2,0,1,0,0,0,4,3,0,2,0,1,0,0,0,0,5,4,0,3,0,2,0,0,0,1 %N A143540 Triangle read by rows, (A143538)^2; 1<=k<=n. %C A143540 Row sums = A079551: (0, 1, 3, 3, 6, 6, 10,...). %F A143540 Square of triangle A143538. %e A143540 First few rows of the triangle = %e A143540 0; %e A143540 0, 1; %e A143540 0, 2, 1; %e A143540 0, 2, 1, 0; %e A143540 0, 3, 2, 0, 1; %e A143540 0, 3, 2, 0, 1, 0 %e A143540 0, 4, 3, 0, 2, 0, 1; %e A143540 ... %Y A143540 Cf. A143538, A079551. %K A143540 nonn,tabl %O A143540 1,5 %A A143540 _Gary W. Adamson_, Aug 23 2008