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Search: id:A060008
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| A060008 |
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9*C(n,4) = 3n(n-1)(n-2)(n-3)/8 |
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+0
5
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| 0, 0, 0, 0, 9, 45, 135, 315, 630, 1134, 1890, 2970, 4455, 6435, 9009, 12285, 16380, 21420, 27540, 34884, 43605, 53865, 65835, 79695, 95634, 113850, 134550, 157950, 184275, 213759, 246645, 283185, 323640, 368280, 417384, 471240, 530145, 594405
(list; graph; listen)
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OFFSET
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0,5
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COMMENT
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Number of permutations of n letters where exactly four change position.
Number of permutations of (4 to infinity) distinct letters (ABC......XYW etc.) each with 1 copies such that there are n-4 fixed points. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 15 2006
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FORMULA
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Equals 3*A050534. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Feb 12 2007
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EXAMPLE
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a(6) = 135 since there are 15 ways to choose the four points that move and 9 ways to move them and 15*9=135.
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CROSSREFS
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For changing 0, 1, 2, 3, 4, 5, n-4, n elements see A000012, A000004, A000217 (offset), A007290, A060008, A060836, A000475, A000166. Also see A000332, A008290.
A diagonal of A008291.
Sequence in context: A067536 A139609 A068314 this_sequence A095166 A126899 A008501
Adjacent sequences: A060005 A060006 A060007 this_sequence A060009 A060010 A060011
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KEYWORD
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easy,nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Mar 16 2001
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