|
%I #4 Jun 16 2016 23:27:30
%S 1,2,12,3342,178985294,2483527716080119,14325590005802419238355799,
%T 50976900301828909677297289506452525838,
%U 155682086691137998248942804080553139214788341933547854
%N Number of nonisomorphic groupoids with <= n elements.
%C The number of isomorphism classes of closed binary operations on sets of order <= n. See formulas by Christian G. Bower in A001329 Number of nonisomorphic groupoids with n elements.
%F a(n) = SUM[i=0..n] A001329(i). a(n) = SUM[i=0..n] (A079173(i)+A027851(i)). a(n) = SUM[i=0..n] (A079177(i)+A079180(i)). a(n) = SUM[i=0..n] (A079183(i)+A001425(i)). a(n) = SUM[i=0..n] (A079187(i)+A079190(i)). a(n) = SUM[i=0..n] (A079193(i)+A079196(i)+A079199(i)+A001426(i)).
%e a(5) = 1 + 1 + 10 + 3330 + 178981952 + 2483527537094825 = 2483527716080119 is prime.
%Y Cf. A001424, A001425, A002489, A006448, A029850, A030245-A030265, A030271, A038015-A038023.
%K nonn
%O 0,2
%A _Jonathan Vos Post_, May 06 2006
| 