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Search: id:A018932
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| A018932 |
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The number of permutations of n cards in which 4 will be the next hit after 2. |
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+0
2
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| 0, 3, 10, 60, 408, 3120, 26640, 252000, 2620800, 29756160, 366508800, 4869849600, 69455232000, 1058593536000, 17174123366400, 295534407168000, 5377157001216000, 103149354147840000, 2080771454361600000
(list; graph; listen)
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OFFSET
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4,2
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COMMENT
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From the game of Mousetrap.
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REFERENCES
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Mundfrom, Daniel J.; A problem in permutations: the game of `Mousetrap'. European J. Combin. 15 (1994), no. 6, 555-560.
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LINKS
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D. J. Mundform, A problem of permutations: the Game of 'Moustrap', Eur. J. Combinat. 15 (1994) 555-560.
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FORMULA
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a(n)=(n-2)!-3(n-3)!+2(n-3)! if n>5. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 02 2008
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CROSSREFS
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Cf. A002468.
Sequence in context: A159321 A158873 A103591 this_sequence A111562 A009654 A013565
Adjacent sequences: A018929 A018930 A018931 this_sequence A018933 A018934 A018935
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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Changed offset to 4. More terms, better definition and link from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 02 2008
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