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 A363036 #27 May 18 2023 10:41:37 %S A363036 1,1,1,1,9,6,1,49,306,114,1,225,8550,26376,5256,1,961,194850,3311250, %T A363036 4669200,507720 %N A363036 Triangular array read by rows. T(n,k) is the number of regular elements in the semigroup of all binary relations on [n] that have rank k, n>=0, 0<=k<=n. %H A363036 K. K.-H. Butler and G. Markowsky, <a href="https://www.koreascience.or.kr/article/JAKO197225748110925.pdf">The Number of Maximal Subgroups of the Semigroup of Binary Relations</a>, Kyungpook Math. J. Vol 12, June 1972. %e A363036 1; %e A363036 1, 1; %e A363036 1, 9, 6; %e A363036 1, 49, 306, 114; %e A363036 1, 225, 8550, 26376, 5256; %e A363036 1, 961, 194850, 3311250, 4669200, 507720; %e A363036 ... %Y A363036 Cf. A354279 (row sums), A003425 (main diagonal), A060867 (column k=1), A354741. %K A363036 nonn,tabl,more %O A363036 0,5 %A A363036 _Geoffrey Critzer_, May 17 2023