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A229536
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Number of defective 3-colorings of a 3 X n 0..2 array connected horizontally, diagonally and antidiagonally with exactly one mistake, and colors introduced in row-major 0..2 order.
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1
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0, 20, 58, 361, 1588, 7460, 33136, 146300, 634976, 2729872, 11628320, 49175856, 206658752, 863838624, 3594073792, 14892589280, 61487645824, 253053701600, 1038460551744, 4250534994848, 17357200322560, 70727788661344
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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) = 6*a(n-1) - a(n-2) - 28*a(n-3) - 4*a(n-4) + 16*a(n-5) - 4*a(n-6) for n>8.
Empirical g.f.: x^2*(20 - 62*x + 33*x^2 + 40*x^3 - 3*x^4 - 16*x^5 + 4*x^6) / (1 - 3*x - 4*x^2 + 2*x^3)^2. - Colin Barker, Sep 18 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..0..1....0..1..0..2....0..1..2..1....0..1..2..1....0..1..2..1
..0..2..0..2....0..2..1..2....0..1..0..1....0..1..2..1....2..0..2..1
..2..1..0..1....0..2..0..2....2..2..0..1....2..0..2..0....2..0..2..1
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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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