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Search: id:A145222
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| A145222 |
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a(n) is the number of odd permutations (of an n-set) with exactly 1 fixed point. |
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+0
2
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| 0, 0, 3, 0, 30, 120, 945, 7392, 66780, 667440, 7342335, 88107360, 1145396538, 16035550440
(list; graph; listen)
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OFFSET
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1,3
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REFERENCES
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Ali, Bashir and Umar, A., "Some combinatorial properties of the alternating group". Southeast Asian Bulletin Math. 32 (2008), 823-830.
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FORMULA
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a(n)=n*A145221(n-1), (n > 0)
Egf.: ((x^3)e^(-x))/2(1-x)
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EXAMPLE
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a(3) = 3 because there are exactly 3 odd permutations (of a 3-set) having 1 fixed point, namely: (12), (13), (23).
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CROSSREFS
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A145221
Sequence in context: A138543 A143769 A007415 this_sequence A058833 A012775 A157308
Adjacent sequences: A145219 A145220 A145221 this_sequence A145223 A145224 A145225
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KEYWORD
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nonn
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AUTHOR
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A. Umar (aumarh(AT)squ.edu.om), Oct 09 2008
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