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 A038021 #10 Dec 19 2015 09:50:55 %S A038021 1,0,1,1,2,1,38,57,27,7,13872,18544,9280,2080,192,83360520,104208775, %T A038021 52110500,13035000,1632750,82355 %N A038021 Triangle: T(n,k), k<=n: commutative groupoids with n elements and k idempotents. %H A038021 <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a> %Y A038021 Cf. A001329, A001425, A030257, A030260, A030263. %K A038021 nonn,tabl,more %O A038021 0,5 %A A038021 _Christian G. Bower_, May 15 1998