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A261766
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a(n) is the number of partial derangements of an n-set with at least one orbit of size exactly n.
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5
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1, 0, 3, 8, 30, 144, 840, 5760, 45360, 403200, 3991680, 43545600, 518918400, 6706022400, 93405312000, 1394852659200, 22230464256000, 376610217984000, 6758061133824000, 128047474114560000, 2554547108585472000, 53523844179886080000, 1175091669949317120000
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OFFSET
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0,3
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REFERENCES
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A. Laradji and A. Umar, On the number of subpermutations with fixed orbit size, Ars Combinatoria, 109 (2013), 447-460.
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LINKS
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FORMULA
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EXAMPLE
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a(3) = 8 because there are 8 partial derangements on {1,2,3} with at least one orbit of size 3 namely: (1,2) --> (2,3), (1,2) --> (3,1), (1,3) --> (2,1), (1,3) --> (3,2), (2,3) --> (3,1), (2,3) --> (1,2), (1,2,3) --> (2,3,1), (1,2,3) --> (3,1,2).
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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