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Search: id:A007060
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| A007060 |
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Number of ways n couples can sit in a row without any spouses next to each other. |
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+0
2
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| 1, 0, 8, 240, 13824, 1263360, 168422400, 30865121280, 7445355724800, 2287168006717440, 871804170613555200, 403779880746418176000, 223346806774106790297600, 145427383048755178635264000
(list; graph; listen)
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OFFSET
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0,3
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LINKS
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Eric Weisstein's World of Mathematics, Cocktail Party Graph
Eric Weisstein's World of Mathematics, Hamiltonian Path
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FORMULA
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a(n) = (Pi*BesselI(n+1/2,1)*(-1)^n+BesselK(n+1/2,1))*exp(-1)*(2/Pi)^(1/2)*2^n*n! [From Mark van Hoeij (hoeij(AT)math.fsu.edu), Nov 12 2009]
a(n) = (-1)^n*2^n*n!*A000806(n), n>0. [From Vladeta Jovovic (vladeta(AT)eunet.rs), Nov 19 2009]
a(n) = n!*hypergeom([ -n, n+1],[],1/2)*(-2)^n [From Mark van Hoeij (hoeij(AT)math.fsu.edu), Nov 13 2009]
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MAPLE
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sum((-1)^i*binomial(n, i)*(2^i*abs((2*n-i))!), i=0..n);
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CROSSREFS
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Sequence in context: A134504 A145418 A067360 this_sequence A158263 A115613 A085524
Adjacent sequences: A007057 A007058 A007059 this_sequence A007061 A007062 A007063
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KEYWORD
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nonn,easy,nice,new
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AUTHOR
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David.Roberts.Keeney(AT)directory.Reed.EDU (David Roberts Keeney)
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EXTENSIONS
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More terms from Michel ten Voorde (seqfan(AT)tenvoorde.org) Apr 11 2001
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