A079199 Number of isomorphism classes of associative non-commutative closed binary operations on a set of order n.

0, 2, 12, 130, 1590, 26491, 1610381, 3683808612, 105978166390449

Offset: 1

Author

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

Keywords

• nonn

Comments

A079193(n)+A079196(n)+A079199(n)+A001426(n)=A001329(n).

Each a(n) is equal to the sum of the elements in row n of A079200.

Since this is the number of nonisomorphic noncommutative semigroups of order n, A079199(n)=A027851(n)-A001426(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. A001426, A027851, A079193, A079196, A079198, A079200.

Extensions

Added terms a(5)-a(9). - Stanislav Sykora, Apr 03 2016