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A229473
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Number of defective 4-colorings of an n X 2 0..3 array connected horizontally, antidiagonally and vertically with exactly one mistake, and colors introduced in row-major 0..3 order.
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1
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1, 6, 42, 248, 1312, 6528, 31232, 145408, 663552, 2981888, 13238272, 58195968, 253755392, 1098907648, 4731174912, 20266876928, 86436216832, 367219703808, 1554778161152, 6562710028288, 27625229647872, 115998476730368
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OFFSET
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1,2
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LINKS
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FORMULA
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Empirical: a(n) = 8*a(n-1) - 16*a(n-2) for n>4.
G.f.: x*(1 - 2*x + 10*x^2 + 8*x^3) / (1 - 4*x)^2.
a(n) = 2^(2*n-5) * (10*n-9) for n>2.
(End)
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EXAMPLE
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Some solutions for n=4:
..0..1....0..0....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..0
..2..0....1..2....2..0....2..2....2..3....2..0....2..0....2..3....2..1....1..2
..0..2....3..1....1..2....3..0....0..2....2..3....0..3....1..2....0..3....3..0
..3..0....2..3....2..0....2..3....2..0....1..2....2..0....1..0....2..0....1..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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