A058166 Triangle read by rows: T(n,k) = number of labeled semigroups of order n with k idempotents.

1, 4, 4, 24, 54, 35, 356, 1044, 1488, 604, 16585, 31620, 60900, 57900, 16727, 3461916, 1699290, 3345420, 4744380, 3128880, 681232, 6058301508, 265521354, 263429355, 439698420, 455785470, 222132666, 38187291

Offset

1,2

Links

Table of n, a(n) for n=1..28.

Index entries for sequences related to semigroups

Example

Triangle begins:
        1;
        4,       4;
       24,      54,      35;
      356,    1044,    1488,     604;
    16585,   31620,   60900,   57900,   16727;
  3461916, 1699290, 3345420, 4744380, 3128880, 681232;
  ...

Crossrefs

Row sums give A023814.

Main diagonal is A351730.

Cf. A058108 (isomorphism classes), A058167, A058157, A058158.

Sequence in context: A131978 A049614 A269186 * A092897 A269152 A269097

Adjacent sequences: A058163 A058164 A058165 * A058167 A058168 A058169

Keyword

nonn,tabl,hard

Author

Christian G. Bower, Nov 15 2000

Status

approved