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%I #13 Jan 27 2022 18:18:43
%S 1,2,1,5,5,2,16,23,14,5,62,106,93,49,15,342,544,582,422,200,53,3435,
%T 3380,3773,3360,2178,943,222,97061,30788,27222,26625,21283,12676,5072,
%U 1078
%N Triangle read by rows: T(n,k) is the number of isomorphism classes of commutative semigroups of order n with k idempotents.
%H <a href="/index/Se#semigroups">Index entries for sequences related to semigroups</a>
%e Triangle begins:
%e 1;
%e 2, 1;
%e 5, 5, 2;
%e 16, 23, 14, 5;
%e 62, 106, 93, 49, 15;
%e ...
%Y Row sums give A001426.
%Y Main diagonal is A006966(n+1).
%Y Column 1 is A058117.
%Y The labeled version is A058167.
%Y Cf. A058108, A058142.
%K nonn,tabl,hard,more
%O 1,2
%A _Christian G. Bower_, Nov 09 2000
%E a(29)-a(36) from _Andrew Howroyd_, Jan 27 2022
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