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A001424 Number of nonisomorphic and nonantiisomorphic groupoids with n elements.
(Formerly M4465 N1894)
4
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
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.
FORMULA
a(n) = (A001329(n) + A029850(n))/2
CROSSREFS
Sequence in context: A284705 A203012 A203697 * A055318 A117661 A206459
KEYWORD
nonn
AUTHOR
EXTENSIONS
Better description and corrected 4th term from Christian G. Bower, Jan 15 1998. More terms, Jun 15 1998.
STATUS
approved

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Last modified June 18 07:40 EDT 2024. Contains 373469 sequences. (Running on oeis4.)