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 A351731 #5 Feb 17 2022 14:19:20 %S A351731 1,2,12,140,3020,100362,4768624,305498328,25293331098,2619996058190 %N A351731 Number of labeled idempotent monoids of order n. %F A351731 a(n) = n * A351731(n-1). %Y A351731 Main diagonal of A058157. %Y A351731 Cf. A058153, A351730. %K A351731 nonn,hard,more %O A351731 1,2 %A A351731 _Andrew Howroyd_, Feb 17 2022