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 A354279 #11 Jun 17 2022 15:55:46 %S A354279 1,2,16,470,40408,8683982 %N A354279 Number of regular elements in the semigroup of all binary relations on [n]. %C A354279 Let S be a semigroup. An element A in S is regular iff A = A*B*A for some B in S. An element in the semigroup of all binary relations is regular iff its row space forms a distributive lattice under set inclusion. %H A354279 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. %Y A354279 Cf. A003425. %K A354279 nonn,more %O A354279 0,2 %A A354279 _Geoffrey Critzer_, May 22 2022