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A233252
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Number of n X 4 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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10, 1184, 166400, 23896064, 3439984640, 495341010944, 71328837140480, 10271348253261824, 1479074079750225920, 212986666384520904704, 30670079941778824232960, 4416491511334675712835584
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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) = 160*a(n-1) - 2304*a(n-2).
G.f.: 2*x*(5 - 208*x) / ((1 - 16*x)*(1 - 144*x)).
a(n) = 2^(4*n-3) * (4*9^n+9) / 9.
(End)
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EXAMPLE
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Some solutions for n=2:
..0..1..2..1....0..1..0..1....0..1..2..4....0..1..0..1....0..1..2..4
..0..1..3..0....0..2..5..3....3..1..5..4....5..2..5..3....3..4..5..3
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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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