A079197 - OEIS

%I #6 Jul 10 2011 18:42:31

%S 0,0,1,1,4,5,107,0,0,0,5,0,28,488,43389

%N Number of isomorphism classes of non-associative commutative closed binary operations on a set of order n, listed by class size.

%C A079194(n)+A079197(n)+A079200(n)+A079201(n)=A079171(n).

%C Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!)

%C First four rows: 0; 0,1; 1,4,5,107; 0,0,0,5,0,28,488,43389

%C A079195(x) is equal to the sum of the products of each element in row x of this sequence and the corresponding element of A079210.

%C The sum of each row x of this sequence is given by A079196(x).

%H C. van den Bosch, <a href="http://cosmos.ucc.ie/~cjvdb1/html/binops.shtml">Closed binary operations on small sets</a>

%H <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a>

%Y Cf. A079194, A079198, A079199, A079200, A079201.

%K nonn,tabf

%O 1,5

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