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A090599 Number of n-element labeled commutative groupoids with an identity. 1
1, 4, 81, 16384, 48828125, 2821109907456, 3909821048582988049, 154742504910672534362390528, 202755595904452569706561330872953769, 10000000000000000000000000000000000000000000000 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

Also labeled commutative groupoids with an absorbant (zero) element.

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) = n^(1+binomial(n, 2))

CROSSREFS

a(n) = A076113(n)*n. Cf. A038017.

Sequence in context: A202831 A128911 A068087 * A133396 A158981 A007154

Adjacent sequences:  A090596 A090597 A090598 * A090600 A090601 A090602

KEYWORD

nonn

AUTHOR

Christian G. Bower (bowerc(AT)usa.net), Dec 05 2003

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Last modified February 16 13:48 EST 2012. Contains 205921 sequences.