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A079200
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Number of isomorphism classes of associative non-commutative closed binary operations on a set of order n, listed by class size.
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6
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0, 0, 2, 0, 2, 0, 4, 6, 2, 0, 0, 4, 5, 0, 46, 73, 2, 0, 0, 0, 4, 0, 0, 8, 0, 2, 36, 0, 43, 2, 473, 1020, 2, 0, 0, 0, 0, 4, 0, 0, 0, 0, 8, 0, 0, 4, 0, 36, 0, 0, 0, 0, 86, 0, 0, 38, 415, 0, 758, 32, 6682, 18426, 2, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8
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OFFSET
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0,3
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COMMENTS
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Number of elements per row: 1,1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!).
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LINKS
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FORMULA
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EXAMPLE
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Triangle T(n,k) begins:
0;
0;
2, 0;
2, 0, 4, 6;
2, 0, 0, 4, 5, 0, 46, 73;
2, 0, 0, 0, 4, 0, 0, 8, 0, 2, 36, 0, 43, 2, 473, 1020;
...
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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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EXTENSIONS
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a(0)=0 prepended and terms a(16) and beyond from Andrew Howroyd, Jan 26 2022
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STATUS
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approved
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