A079199 - OEIS

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A079199

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

10

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

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OFFSET

1,2

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

Table of n, a(n) for n=1..9.

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.

Sequence in context: A098628 A123553 A354493 * A303926 A214759 A365601

Adjacent sequences: A079196 A079197 A079198 * A079200 A079201 A079202

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

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

STATUS

approved