0,3

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

Grillet, P.A., Computing Finite Commutative Semigroups, Semigroup Forum 53 (1996), 140-154.

Grillet, P.A., Computing Finite Commutative Semigroups: Part II, Semigroup Forum 67 (2003), 159-184.

H. Juergensen and P. Wick, Die Halbgruppen von Ordnungen <= 7, Semigroup Forum, 14 (1977), 69-79.

R. J. Plemmons, There are 15973 semigroups of order 6, Math. Algor., 2 (1967), 2-17; 3 (1968), 23.

R. J. Plemmons, Cayley Tables for All Semigroups of Order Less Than 7. Department of Mathematics, Auburn Univ., 1965.

Satoh, S.; Yama, K.; and Tokizawa, M., Semigroups of order 8, Semigroup Forum 49 (1994), 7-29.

Eric Postpischil Posting to sci.math newsgroup, May 21 1990

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Index entries for sequences related to semigroups

Cf. A001423, A023815, A027851, A058105, A058116.

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

Adjacent sequences: A001423 A001424 A001425 this_sequence A001427 A001428 A001429

Sequence in context: A090363 A115086 A125276 this_sequence A059440 A020075 A020030

nonn,nice,hard

N. J. A. Sloane (njas(AT)research.att.com).

a(8) (from the Satoh et al. paper) supplied by Richard Schroeppel, Jul 22 2005

a(9) and a(10) from Grillet references sent by Jens Zumbragel (jzumbr(AT)math.unizh.ch), Jun 14 2006