A058116 Triangle read by rows: T(n,k) is the number of isomorphism classes of commutative semigroups of order n with k idempotents.

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

Offset: 1

Author

Christian G. Bower, Nov 09 2000

Keywords

• nonn
• tabl
• hard
• more

Examples

			Triangle begins:
   1;
   2,   1;
   5,   5,  2;
  16,  23, 14,  5;
  62, 106, 93, 49, 15;
  ...
		

Links

• Index entries for sequences related to semigroups

Crossrefs

Row sums give A001426.

Main diagonal is A006966(n+1).

Column 1 is A058117.

The labeled version is A058167.

Cf. A058108, A058142.

Extensions

a(29)-a(36) from Andrew Howroyd, Jan 27 2022