OFFSET
1,2
LINKS
Gary Gordon, Elizabeth McMahon, Moving faces to other places: Facet derangements, arXiv:0906.4253 [math.CO], 2009.
Gary Gordon and Elizabeth McMahon, Moving faces to other places: facet derangements, Amer. Math. Monthly, 117 (2010), 865-88.
FORMULA
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.
From Peter Luschny, May 09 2017: (Start)
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)
EXAMPLE
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.
MAPLE
A161936 := n -> (2^n*GAMMA(n+1, -1/2)/exp(1/2)+(-1)^n)/2:
seq(A161936(n), n=1..20); # Peter Luschny, May 09 2017
MATHEMATICA
a[n_] := (-1)^n*(1 - n*HypergeometricPFQ[{1, 1 - n}, {}, 2]);
Array[a, 20] (* Jean-François Alcover, Jul 14 2018, after Peter Luschny *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Elizabeth McMahon, Gary Gordon (mcmahone(AT)lafayette.edu), Jun 29 2009
EXTENSIONS
More terms from Peter Luschny, May 09 2017
STATUS
approved