A079209 Number of isomorphism classes of associative commutative non-anti-associative non-anti-commutative closed binary operations on a set of order n, listed by class size.

0, 0, 3, 0, 0, 3, 9, 0, 0, 0, 3, 0, 0, 16, 39

Offset

1,3

Comments

A079202(n)+A079203(n)+A079204(n)+A079205(n)+A079197(n)+A079207(n)+A079208(n)+A079209(n)+A063524(n)=A079171(n)

Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!)

First four rows: 0; 0,3; 0,0,3,9; 0,0,0,3,0,0,16,39

A079244(x) is equal to the sum of the products of each element in row x of this sequence and the corresponding element of A079210.

The sum of each row x of this sequence is given by A079245(x).

Links

Table of n, a(n) for n=1..15.

C. van den Bosch, Closed binary operations on small sets

Index entries for sequences related to semigroups

Crossrefs

Cf. A079202, A079203, A079204, A079205, A079197, A079207, A079208, A079244, A079245.

Sequence in context: A363035 A151665 A171793 * A079201 A279368 A021773

Adjacent sequences: A079206 A079207 A079208 * A079210 A079211 A079212

Keyword

nonn,tabf

Author

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

Status

approved