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Search: id:A055658
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| A055658 |
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Number of (3,n)-partitions of a chain of length n^2. |
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+0
1
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| 0, 0, 1, 35, 286, 1330, 4495, 12341, 29260, 62196, 121485, 221815, 383306, 632710, 1004731, 1543465, 2303960, 3353896, 4775385, 6666891, 9145270, 12347930, 16435111, 21592285, 28032676, 35999900, 45770725, 57657951, 72013410
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OFFSET
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1,4
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COMMENT
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a (k,n)-partition of a chain C is a chain of k intervals of C of length n
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FORMULA
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a(n)=1/6*(n-1)*(n-2)*(n^2-3*n+3)*(n^2-3*n+1)
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EXAMPLE
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a(3)=1 because in the linearly ordered set {1,..,9} we can choose in just one way 3 successive blocks of 3 consecutive elements
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CROSSREFS
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Sequence in context: A113941 A067238 A090646 this_sequence A125773 A071697 A027792
Adjacent sequences: A055655 A055656 A055657 this_sequence A055659 A055660 A055661
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KEYWORD
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nonn
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AUTHOR
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Paolo Dominici (pl.dm(AT)libero.it), Jun 07 2000
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