cp's OEIS Frontend

A001424 Number of nonisomorphic and nonantiisomorphic groupoids with n elements.

%I A001424 M4465 N1894 #28 Feb 16 2025 08:32:23
%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, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A001424 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (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?&amp;hl=en&amp;lr=&amp;ie=UTF-8&amp;selm=11802%40shlump.nac.dec.com&amp;rnum=2">Posting to sci.math newsgroup, May 21 1990</a>
%H A001424 N. J. A. Sloane, <a href="/A001329/a001329.jpg">Overview of A001329, A001423-A001428, A258719, A258720.</a>
%H A001424 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 A001424 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Groupoid.html">Groupoid.</a>
%H A001424 <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a>
%F A001424 a(n) = (A001329(n) + A029850(n))/2
%Y A001424 Cf. A001329, A029850.
%K A001424 nonn
%O A001424 0,3
%A A001424 _N. J. A. Sloane_
%E A001424 Better description and corrected 4th term from _Christian G. Bower_, Jan 15 1998. More terms, Jun 15 1998.