A079199 - OEIS

%I #10 Apr 03 2016 20:19:48

%S 0,2,12,130,1590,26491,1610381,3683808612,105978166390449

%N Number of isomorphism classes of associative non-commutative closed binary operations on a set of order n.

%C A079193(n)+A079196(n)+A079199(n)+A001426(n)=A001329(n).

%C Each a(n) is equal to the sum of the elements in row n of A079200.

%C Since this is the number of nonisomorphic noncommutative semigroups of order n, A079199(n)=A027851(n)-A001426(n). - _Stanislav Sykora_, Apr 03 2016

%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/Se#semigroups">Index entries for sequences related to semigroups</a>

%Y Cf. A001426, A027851, A079193, A079196, A079198, A079200.

%K nonn

%O 1,2

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

%E Added terms a(5)-a(9). - _Stanislav Sykora_, Apr 03 2016