%I A005591 M4246
%S A005591 6,44,351,3093,33445
%N A005591 Number of semigroups of order n with 3 idempotents, considered to be 
               equivalent when they are isomorphic or anti-isomorphic (by reversal 
               of the operator).
%D A005591 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A005591 H. Juergensen and P. Wick, Die Halbgruppen von Ordnungen <= 7, Semigroup 
               Forum, 14 (1977), 69-79.
%D A005591 R. J. Plemmons, There are 15973 semigroups of order 6, Math. Algor., 
               2 (1967), 2-17; 3 (1968), 23.
%H A005591 <a href="Sindx_Se.html#semigroups">Index entries for sequences related 
               to semigroups</a>
%Y A005591 Column 3 of A058123.
%Y A005591 Sequence in context: A115969 A082412 A108452 this_sequence A052204 A147688 
               A090442
%Y A005591 Adjacent sequences: A005588 A005589 A005590 this_sequence A005592 A005593 
               A005594
%K A005591 nonn
%O A005591 3,1
%A A005591 N. J. A. Sloane (njas(AT)research.att.com).