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A018934
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From the game of Mousetrap.
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2
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0, 0, 0, 2, 8, 42, 256, 1810, 14568, 131642, 1320128, 14551074, 174879880, 2276108362, 31894886208, 478775722802, 7664993150696, 130369025763930, 2347604596782208, 44619881467365442, 892659329531868168
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Number of permutations p of [n] such that p(k) = k+2 for exactly one k in the range 0<k<n-1. - Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 30 2007
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REFERENCES
| Mundfrom, Daniel J.; A problem in permutations: the game of `Mousetrap'. European J. Combin. 15 (1994), no. 6, 555-560.
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FORMULA
| a(n) = (n-2)*A055790(n-2). E.g.f.: 2*x*exp(-x)/(1-x)^3. - Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 30 2007
a(n)=floor((n!+1)/e)-floor(((n-2)!+1)/e), n>2. [From Gary Detlefs (gdetlefs(AT)aol.com), Mar 27 2011]
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CROSSREFS
| Cf. A002468.
Sequence in context: A120916 A133417 A100327 * A107588 A013999 A130649
Adjacent sequences: A018931 A018932 A018933 * A018935 A018936 A018937
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 30 2007, corrected Jan 25 2008
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