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A208421
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Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 0 1 1 vertically.
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1
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9, 81, 261, 1269, 5139, 22509, 95265, 409239, 1746639, 7475751, 31957515, 136685781, 584484003, 2499573411, 10689072525, 45711185121, 195479542125, 835952734845, 3574879817931, 15287675934645, 65376453864249
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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) = 3*a(n-1) + 7*a(n-2) - 6*a(n-3) - 3*a(n-4) + 2*a(n-5).
Empirical g.f.: 9*x*(1 + 6*x - 5*x^2 - 3*x^3 + 2*x^4) / (1 - 3*x - 7*x^2 + 6*x^3 + 3*x^4 - 2*x^5). - Colin Barker, Jul 02 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..0..1....0..1..1..1....0..1..1..0....1..0..1..0....1..0..1..0
..0..1..0..1....1..0..1..0....0..1..1..0....1..1..0..0....1..0..1..1
..1..0..1..0....0..1..0..0....1..0..1..1....1..0..1..1....1..1..1..0
..0..1..0..1....1..0..1..1....0..1..0..0....1..1..0..0....1..0..1..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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