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A090600
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Number of n-element groupoids with an identity, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).
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0
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1, 2, 30, 22456, 3179460875, 118459556737869096, 1841479754519556293280702095, 17699004125822025124951660289473617122688, 146207646053305863964379580591072585873215024249550168360
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OFFSET
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1,2
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COMMENTS
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Also partial groupoids with n-1 elements or groupoids with an absorbant (zero) element with n elements in each case the same equivalence.
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LINKS
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Eric Weisstein's World of Mathematics, Groupoid.
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FORMULA
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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