A079198 Number of associative non-commutative closed binary operations on a set of order n.

0, 2, 50, 2352, 153002, 15876046, 7676692858

Offset: 1

Author

Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003

Keywords

• nonn
• more

Comments

a(n) + A079192(n) + A079195(n) + A023815(n) = A002489(n).

Each a(n) is equal to the sum of the products of each element in row n of A079200 and the corresponding element of A079210.

Since this is the number of labeled noncommutative semigroups on an n-set, a(n) = A023814(n)-A023815(n). - Stanislav Sykora, Apr 03 2016

Links

• C. van den Bosch, Closed binary operations on small sets
• Index entries for sequences related to semigroups

Crossrefs

Cf. A023814, A023815, A079192, A079195, A079199, A079200.

Extensions

a(5)-a(7) added by Stanislav Sykora, Apr 03 2016