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Search: id:A079201
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| A079201 |
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Number of isomorphism classes of associative commutative closed binary operations on a set of order n, listed by class size. |
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+0
5
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| 1, 0, 3, 0, 0, 3, 9, 0, 0, 0, 3, 0, 0, 16, 39
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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A079194(n)+A079197(n)+A079200(n)+A079201(n)=A079171(n).
Elements per row: 1,2,4,8,16,30,... (given by A027423, number of positive divisors of n!)
First four rows: 1; 0,3; 0,0,3,9; 0,0,0,3,0,0,16,39
A023815(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 of this sequence is given by A001426(x).
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LINKS
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C. van den Bosch, Closed binary operations on small sets
Index entries for sequences related to semigroups
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CROSSREFS
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Cf. A001426, A023815, A079194, A079197, A079200. a(n, A027423(n)) = A058105(n).
Sequence in context: A005082 A050452 A151665 this_sequence A079209 A021773 A133109
Adjacent sequences: A079198 A079199 A079200 this_sequence A079202 A079203 A079204
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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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