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A207347
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Number of 3 X n 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 0 and 1 1 1 vertically.
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1
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6, 36, 84, 192, 426, 858, 1704, 3330, 6390, 12150, 22938, 43044, 80424, 149766, 278160, 515568, 954072, 1763304, 3255666, 6006342, 11074116, 20407650, 37592934, 69228330, 127454070, 234605316, 431771328, 794539482, 1461954876, 2689788048
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) + a(n-3) - 2*a(n-4) - a(n-5) - a(n-6) for n>7.
Empirical g.f.: 6*x*(1 + x)*(1 + 3*x - x^2 + 4*x^3 - x^4 + x^5) / ((1 - x - x^3)*(1 - x - x^2 - x^3)). - Colin Barker, Jun 22 2018
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EXAMPLE
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Some solutions for n=4:
..1..0..0..1....0..0..1..0....0..0..1..0....1..1..0..0....1..0..1..0
..1..0..1..0....0..1..0..0....1..0..0..1....1..1..1..1....0..0..1..0
..0..1..0..1....1..1..0..1....0..1..0..1....0..0..1..0....0..1..0..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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