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A161936
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The number of direct isometries that are derangements of the (n-1)-dimensional facets of an n-cube.
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3
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0, 3, 14, 117, 1164, 13975, 195642, 3130281, 56345048, 1126900971, 24791821350, 595003712413, 15470096522724, 433162702636287, 12994881079088594, 415836194530835025, 14138430614048390832, 508983502105742069971, 19341373080018198658878, 773654923200727946355141
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OFFSET
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1,2
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COMMENTS
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a(n) plays the same role as A003221 plays for the derangement numbers A000166.
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LINKS
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FORMULA
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a(n) = (b(n) + (-1)^n)/2, where b(n) is sequence A000354, i.e., the number of (n-1)-dimensional facet derangements of an n-cube.
a(n) = (-1)^n*(1-n*hypergeom([1,1-n],[],2)).
a(n) = (2^n*Gamma(n+1,-1/2)/exp(1/2)+(-1)^n)/2. (End)
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EXAMPLE
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For a square, the 3 rotations are direct edge derangements. For a 3-cube, the 6 edge-centered rotations and the 8 vertex-centered rotations are direct face derangements.
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MAPLE
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A161936 := n -> (2^n*GAMMA(n+1, -1/2)/exp(1/2)+(-1)^n)/2:
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MATHEMATICA
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a[n_] := (-1)^n*(1 - n*HypergeometricPFQ[{1, 1 - n}, {}, 2]);
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Elizabeth McMahon, Gary Gordon (mcmahone(AT)lafayette.edu), Jun 29 2009
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EXTENSIONS
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STATUS
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approved
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