

A023815


Number of binary operations on an nset that are commutative and associative; labeled commutative semigroups.


10




OFFSET

0,3


LINKS

Table of n, a(n) for n=0..7.
Eric Postpischil Posting to sci.math newsgroup, May 21 1990
Amit Sehgal, Sunil Kumar, Sarita, Yashpal, Commutative Associative Binary Operations on a Set with Five Elements, J. Phys.: Conf. Ser. (2018) 1000 012063
Eric Weisstein's World of Mathematics, Semigroup.
Index entries for sequences related to semigroups


CROSSREFS

Cf. A001423, A001426, A023813, A023814, A027851.
a(n)+A079192(n)+A079195(n)+A079198(n)=A002489(n)
Sequence in context: A295241 A271607 A079244 * A249590 A034665 A218383
Adjacent sequences: A023812 A023813 A023814 * A023816 A023817 A023818


KEYWORD

nonn


AUTHOR

Lyle Ramshaw (ramshaw(AT)pa.dec.com)


STATUS

approved



