%I #6 Jul 10 2011 18:42:30
%S 1,4,6,3,12,78,3237,2,1,14,30,275,495,48810,178932325
%N Number of isomorphism classes of closed binary operations (groupoids) on a set of order n, listed by class size.
%C Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!)
%C First four rows: 1; 4,6; 3,12,78,3237; 2,1,14,30,275,495,48810,178932325
%C A002489(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 is given by A001329(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. A002489, A001329. a(n, A027423(n)) = A030245(n).
%K nonn,tabf
%O 1,2
%A Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003