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 A058158 #10 Feb 17 2022 14:19:39 %S A058158 1,1,1,1,6,4,4,45,72,35,6,528,1308,1676,604,80,19935,39700,70170, %T A058158 62060,16727,120,3599436,1969470,3829000,5167800,3260382,681232,2760, %U A058158 6085914205,281840664,294812385,481221020,482447637,228315640,38187291 %N A058158 Triangle read by rows: T(n,k) is the number of labeled monoids of order n with k idempotents and a fixed identity. %H A058158 <a href="/index/Mo#monoids">Index entries for sequences related to monoids</a> %F A058158 T(n,k) = A058157(n,k)/n. %e A058158 Triangle begins: %e A058158 1; %e A058158 1, 1; %e A058158 1, 6, 4; %e A058158 4, 45, 72, 35; %e A058158 6, 528, 1308, 1676, 604; %e A058158 80, 19935, 39700, 70170, 62060, 16727; %e A058158 ... %Y A058158 Row sums give A058154. %Y A058158 Column 1: A058163. %Y A058158 Main diagonal is A351730(n-1). %Y A058158 Cf. A058137 (isomorphism classes), A058157, A058160 (commutative), A058166. %K A058158 nonn,tabl %O A058158 1,5 %A A058158 _Christian G. Bower_, Nov 14 2000 %E A058158 a(30)-a(36) from _Andrew Howroyd_, Feb 15 2022