%I A001424 M4465 N1894
%S A001424 1,1,7,1734,89521056,1241763995193675,7162795001695681351632672,
%T A001424 25488450150907292192918677242007992558,
%U A001424 77841043345568973636021269757801814299054870565039692
%N A001424 Number of nonisomorphic and nonantiisomorphic groupoids with n elements.
%D A001424 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A001424 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A001424 T. Tamura, Some contributions of computation to semigroups and groupoids, 
               pp. 229-261 of J. Leech, editor, Computational Problems in Abstract 
               Algebra. Pergamon, Oxford, 1970.
%H A001424 Eric Postpischil <a href="http://groups.google.com/groups?&hl=en&lr=&ie=UTF-8&selm=11802%40shlump.nac.dec.com\
               &rnum=2">Posting to sci.math newsgroup, May 21 1990</a>
%H A001424 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Groupoid.html">Link to a section of The World of Mathematics.</a>
%H A001424 <a href="Sindx_Gre.html#groupoids">Index entries for sequences related 
               to groupoids</a>
%F A001424 a(n) = (A001329(n) + A029850(n))/2
%Y A001424 Cf. A001329, A029850.
%Y A001424 Sequence in context: A145451 A144676 A125537 this_sequence A055318 A117661 
               A145253
%Y A001424 Adjacent sequences: A001421 A001422 A001423 this_sequence A001425 A001426 
               A001427
%K A001424 nonn
%O A001424 0,3
%A A001424 N. J. A. Sloane (njas(AT)research.att.com).
%E A001424 Better description and corrected 4th term from Christian Bower (bowerc(AT)usa.net), 
               Jan 15 1998. More terms, Jun 15 1998.