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A229751
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Number of defective 4-colorings of an n X 4 0..3 array connected horizontally, vertically, diagonally and antidiagonally with exactly two mistakes, and colors introduced in row-major 0..3 order.
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1
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3, 422, 2347, 6561, 15075, 32548, 69198, 147376, 315786, 680124, 1468934, 3174760, 6855906, 14780020, 31793694, 68231136, 146079674, 312025516, 665011638, 1414360024, 3002176530, 6360776292, 13453355726, 28408158544, 59894811114
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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) = 9*a(n-1) - 33*a(n-2) + 63*a(n-3) - 66*a(n-4) + 36*a(n-5) - 8*a(n-6) for n>11.
Empirical g.f.: x*(3 + 395*x - 1352*x^2 - 825*x^3 + 7089*x^4 - 6731*x^5 + 132*x^6 + 863*x^7 - 58*x^8 - 60*x^9 + 8*x^10) / ((1 - x)^3*(1 - 2*x)^3). - Colin Barker, Sep 21 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..0..2....0..1..0..2....0..1..2..1....0..1..0..0....0..1..2..0
..2..3..0..3....2..3..2..1....2..0..3..0....2..1..2..3....2..3..1..3
..1..1..2..1....0..1..0..3....3..1..2..1....0..3..0..1....0..0..2..0
..3..0..3..0....2..1..2..1....2..0..2..0....2..1..2..3....3..1..3..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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