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A145219
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a(n) is the number of even permutations (of an n-set) with exactly 1 fixed point.
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1
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1, 0, 0, 8, 15, 144, 910, 7440, 66717, 667520, 7342236, 88107480, 1145396395, 16035550608
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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REFERENCES
| 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
| a(n)=n*A003221(n-1), (n > 0).
Egf.: (x(1-x^2/2)e^(-x))/(1-x)
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EXAMPLE
| a(4) = 8 because there are exactly 8 even permutations (of a 4-set) having 1 fixed point, namely: (123), (132), (124), (142), (134), (143), (234), (243).
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CROSSREFS
| A003221
Sequence in context: A110459 A132374 A067686 * A002406 A153700 A190901
Adjacent sequences: A145216 A145217 A145218 * A145220 A145221 A145222
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KEYWORD
| nonn
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AUTHOR
| A. Umar (aumarh(AT)squ.edu.om), Oct 09 2008
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