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 A058144 #5 Mar 30 2012 17:37:11 %S A058144 1,1,1,1,3,1,2,9,6,2,1,28,31,18,6,2,131,160,132,65,19,1,1081,947,917, %T A058144 612,275,68,5 %N A058144 Triangle: Self-converse monoids of order n with k idempotents. %H A058144 <a href="/index/Mo#monoids">Index entries for sequences related to monoids</a> %e A058144 1; 1,1; 1,3,1; 2,9,6,2; 1,28,31,18,6; ... %Y A058144 Row sums give A058132. Main diagonal: A058122(n-1). Columns 1-3: A000001, A058145, A058146. %K A058144 nonn,tabl,more %O A058144 1,5 %A A058144 _Christian G. Bower_, Nov 14 2000