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A060602
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Number of tilings of the d-dimensional zonotope constructed from d+3 vectors.
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10
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8, 24, 62, 148, 338, 752, 1646, 3564, 7658, 16360, 34790, 73700, 155618, 327648, 688094, 1441756, 3014618, 6291416, 13107158, 27262932, 56623058, 117440464, 243269582, 503316428, 1040187338, 2147483592, 4429184966
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OFFSET
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0,1
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COMMENTS
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The zonotope Z(D,d) is the projection of the D-dimensional hypercube onto the d-dimensional space and the tiles are the projections of the d-dimensional faces of the hypercube. Here the codimension, i.e., D-d, is constant = 3 and d >= 0.
Also the number of signotopes on r+2 elements of rank r. A signotope on n elements of rank r is a mapping X:{{1..n} choose r}->{+,-} such that for any r+1 indices I={i_0,...,i_r} with i_0 < i_1 < ... < i_r, the sequence X(I-i_0), X(I-i_1), ..., X(I-i_r) changes its sign at most once (see Felsner-Weil reference). - Manfred Scheucher, Feb 09 2022
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REFERENCES
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A. Bjorner, M. Las Vergnas, B. Sturmfels, N. White and G. M. Ziegler, Oriented Matroids, Encyclopedia of Mathematics 46, Second Edition, Cambridge University Press, 1999.
Victor Reiner, The generalized Baues problem, in New Perspectives in Algebraic Combinatorics (Berkeley, CA, 1996-1997), 293-336, Math. Sci. Res. Inst. Publ., 38, Cambridge Univ. Press, Cambridge, 1999.
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LINKS
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FORMULA
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a(n) = 2*(-3+7*2^n+(-1+2^n)*n).
G.f.: -2*(4*x^3-11*x^2+12*x-4) / ((x-1)^2*(2*x-1)^2). (End)
The above conjectures are correct; see Proposition 7.1 in Ziegler's article. - Manfred Scheucher, Feb 09 2022
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EXAMPLE
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For any Z(D,d), the number of codimension 0 tilings is always 1, with codimension 1 it is 2, with codimension 2 it is 2.D.
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MATHEMATICA
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LinearRecurrence[{6, -13, 12, -4}, {8, 24, 62, 148}, 30] (* Harvey P. Dale, Oct 13 2023 *)
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PROG
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(Python) print([2**(n + 1)*(n + 7) - 2*n - 6 for n in range(100)])
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CROSSREFS
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KEYWORD
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nonn,nice,easy
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AUTHOR
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Matthieu Latapy (latapy(AT)liafa.jussieu.fr), Apr 12 2001
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EXTENSIONS
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STATUS
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approved
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