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A007903
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The number of distinct principal ideals in the semigroup of binary relations on an n-set.
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1
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OFFSET
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1,1
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COMMENTS
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a(n) is the number of Green's J-classes in the semigroup of binary relations on an n-set. - James Mitchell, May 10 2015
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REFERENCES
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K. H. Kim, Boolean Matrix Theory and Applications, Marcel Decker Inc., 1982.
George Markowsky, 1991; Markowsky and Breen, 1993; Breen, 1995.
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LINKS
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FORMULA
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a(n) is asymptotic to 2^(n^2)/n!^2 (from Kim reference). - Geoffrey Critzer, May 14 2023
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CROSSREFS
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KEYWORD
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nonn,hard,more,nice
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AUTHOR
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Michael A Breen (MAB1699(AT)tntech.edu)
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STATUS
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approved
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