Search: id:A118542
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%I A118542
%S A118542 1,2,12,3342,178985294,2483527716080119,14325590005802419238355799,
%T A118542 50976900301828909677297289506452525838,
%U A118542 155682086691137998248942804080553139214788341933547854
%N A118542 Number of nonisomorphic groupoids with <= n elements.
%C A118542 The number of isomorphism classes of closed binary operations on sets 
               of order <= n. See formulae by Christian G. Bower in A001329 Number 
               of nonisomorphic groupoids with n elements.
%F A118542 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 A118542 a(5) = 1 + 1 + 10 + 3330 + 178981952 + 2483527537094825 = 2483527716080119 
               is prime.
%Y A118542 Cf. A001424, A001425, A002489, A006448, A029850, A030245-A030265, A030271, 
               A038015-A038023.
%Y A118542 Sequence in context: A050649 A003042 A000887 this_sequence A007155 A074200 
               A048830
%Y A118542 Adjacent sequences: A118539 A118540 A118541 this_sequence A118543 A118544 
               A118545
%K A118542 nonn
%O A118542 0,2
%A A118542 Jonathan Vos Post (jvospost3(AT)gmail.com), May 06 2006

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