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 A058116 Triangle read by rows: T(n,k) is the number of isomorphism classes of commutative semigroups of order n with k idempotents. 6
 1, 2, 1, 5, 5, 2, 16, 23, 14, 5, 62, 106, 93, 49, 15, 342, 544, 582, 422, 200, 53, 3435, 3380, 3773, 3360, 2178, 943, 222, 97061, 30788, 27222, 26625, 21283, 12676, 5072, 1078 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE Triangle begins:    1;    2,   1;    5,   5,  2;   16,  23, 14,  5;   62, 106, 93, 49, 15;   ... CROSSREFS Row sums give A001426. Main diagonal is A006966(n+1). Column 1 is A058117. The labeled version is A058167. Cf. A058108, A058142. Sequence in context: A248905 A118244 A108410 * A058118 A332632 A124226 Adjacent sequences:  A058113 A058114 A058115 * A058117 A058118 A058119 KEYWORD nonn,tabl,hard,more AUTHOR Christian G. Bower, Nov 09 2000 EXTENSIONS a(29)-a(36) from Andrew Howroyd, Jan 27 2022 STATUS approved

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Last modified August 16 22:14 EDT 2022. Contains 356169 sequences. (Running on oeis4.)