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A079171
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Number of isomorphism classes of closed binary operations (groupoids) on a set of order n, listed by class size.
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20
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1, 4, 6, 3, 12, 78, 3237, 2, 1, 14, 30, 275, 495, 48810, 178932325
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OFFSET
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1,2
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COMMENTS
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Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!)
First four rows: 1; 4,6; 3,12,78,3237; 2,1,14,30,275,495,48810,178932325
A002489(x) is equal to the sum of the products of each element in row x of this sequence and the corresponding element of A079210.
The sum of each row x is given by A001329(x).
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LINKS
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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Christian van den Bosch (cjb(AT)cjb.ie), Jan 03 2003
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STATUS
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approved
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