A001424 - OEIS

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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; 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	`Eric Postpischil Posting to sci.math newsgroup, May 21 1990` `Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.` `Index entries for sequences related to groupoids`
	FORMULA	`a(n) = (A001329(n) + A029850(n))/2`
	CROSSREFS	`Cf. A001329, A029850.` `Sequence in context: A125537 A203012 A203697 * A055318 A117661 A206459` `Adjacent sequences: A001421 A001422 A001423 * A001425 A001426 A001427`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`
	EXTENSIONS	`Better description and corrected 4th term from Christian Bower (bowerc(AT)usa.net), Jan 15 1998. More terms, Jun 15 1998.`

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Last modified February 16 21:51 EST 2012. Contains 205978 sequences.