%I M4465 N1894 #27 Dec 23 2021 23:02:37
%S 1,1,7,1734,89521056,1241763995193675,7162795001695681351632672,
%T 25488450150907292192918677242007992558,
%U 77841043345568973636021269757801814299054870565039692
%N Number of nonisomorphic and nonantiisomorphic groupoids with n elements.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%D 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 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 N. J. A. Sloane, <a href="/A001329/a001329.jpg">Overview of A001329, A001423-A001428, A258719, A258720.</a>
%H T. Tamura, <a href="/A001329/a001329.pdf">Some contributions of computation to semigroups and groupoids</a>, pp. 229-261 of J. Leech, editor, Computational Problems in Abstract Algebra. Pergamon, Oxford, 1970. (Annotated and scanned copy)
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Groupoid.html">Groupoid.</a>
%H <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a>
%F a(n) = (A001329(n) + A029850(n))/2
%Y Cf. A001329, A029850.
%K nonn
%O 0,3
%A _N. J. A. Sloane_
%E Better description and corrected 4th term from _Christian G. Bower_, Jan 15 1998. More terms, Jun 15 1998.