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A118542
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Number of nonisomorphic groupoids with <= n elements.
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0
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1, 2, 12, 3342, 178985294, 2483527716080119, 14325590005802419238355799, 50976900301828909677297289506452525838, 155682086691137998248942804080553139214788341933547854
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OFFSET
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0,2
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COMMENTS
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The number of isomorphism classes of closed binary operations on sets of order <= n. See formulas by Christian G. Bower in A001329 Number of nonisomorphic groupoids with n elements.
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LINKS
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FORMULA
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EXAMPLE
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a(5) = 1 + 1 + 10 + 3330 + 178981952 + 2483527537094825 = 2483527716080119 is prime.
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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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