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A233257
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Number of 2 X n 0..5 arrays with no element x(i,j) adjacent to itself or value 5-x(i,j) horizontally or antidiagonally, top left element zero, and 1 appearing before 2 3 and 4, and 2 appearing before 3 in row major order (unlabelled 6-colorings with no clashing color pairs).
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1
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3, 10, 104, 1184, 13952, 166400, 1992704, 23896064, 286687232, 3439984640, 41278767104, 495341010944, 5944075354112, 71328837140480, 855945777250304, 10271348253261824, 123256174744174592, 1479074079750225920
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 16*a(n-1) - 48*a(n-2) for n>3.
G.f.: x*(3 - 38*x + 88*x^2) / ((1 - 4*x)*(1 - 12*x)).
a(n) = 2^(2*n-3) * (4*3^n+9) / 9 for n>1.
(End)
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EXAMPLE
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Some solutions for n=5:
..0..1..2..5..3....0..1..2..4..3....0..1..5..4..2....0..1..2..1..0
..0..4..2..1..2....5..1..5..4..2....2..4..3..1..2....2..1..5..4..0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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