A001424 - OEIS

A001424

Number of nonisomorphic and nonantiisomorphic groupoids with n elements.
(Formerly M4465 N1894)

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

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

Table of n, a(n) for n=0..8.

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

FORMULA

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

CROSSREFS

Cf. A001329, A029850.

Sequence in context: A284705 A203012 A203697 * A055318 A117661 A206459

Adjacent sequences: A001421 A001422 A001423 * A001425 A001426 A001427

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

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

STATUS

approved