3,1

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

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.

Index entries for sequences related to semigroups

Column 3 of A058123.

Sequence in context: A115969 A082412 A108452 this_sequence A052204 A147688 A090442

Adjacent sequences: A005588 A005589 A005590 this_sequence A005592 A005593 A005594

nonn

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