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 A058142 #15 Feb 15 2022 13:57:39 %S A058142 1,1,1,1,3,1,2,9,6,2,1,26,30,16,5,1,98,142,111,54,15,1,455,718,713, %T A058142 482,215,53,3,4018,4277,4637,3919,2414,996,222,2,101910,36124,32937, %U A058142 31308,24047,13758,5294,1078,1,10054303,708355,290278,260758,229411,164216,88178,31867,5994 %N A058142 Triangle read by rows: number of commutative monoids of order n with k idempotents. %H A058142 <a href="/index/Mo#monoids">Index entries for sequences related to monoids</a> %e A058142 Triangle begins: %e A058142 1; %e A058142 1, 1; %e A058142 1, 3, 1; %e A058142 2, 9, 6, 2; %e A058142 1, 26, 30, 16, 5; %e A058142 1, 98, 142, 111, 54, 15; %e A058142 ... %Y A058142 Row sums give A058131. %Y A058142 Main diagonal: A006966. %Y A058142 Columns 1..2: A000688, A058143. %Y A058142 Cf. A058116, A058137, A058150, A058159, A058160. %K A058142 nonn,tabl,hard %O A058142 1,5 %A A058142 _Christian G. Bower_, Nov 14 2000 %E A058142 a(30)-a(55) from _Andrew Howroyd_, Feb 15 2022