A001424 Number of nonisomorphic and nonantiisomorphic groupoids with n elements.

1, 1, 7, 1734, 89521056, 1241763995193675, 7162795001695681351632672, 25488450150907292192918677242007992558, 77841043345568973636021269757801814299054870565039692

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

References

• N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
• 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.

Links

• Eric Postpischil Posting to sci.math newsgroup, May 21 1990
• N. J. A. Sloane, Overview of A001329, A001423-A001428, A258719, A258720.
• 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. (Annotated and scanned copy)
• Eric Weisstein's World of Mathematics, Groupoid.
• Index entries for sequences related to groupoids

Crossrefs

Cf. A001329, A029850.

Formula

a(n) = (A001329(n) + A029850(n))/2

Extensions

Better description and corrected 4th term from Christian G. Bower, Jan 15 1998. More terms, Jun 15 1998.