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A207847
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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 1 1 1 vertically.
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1
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10, 100, 240, 780, 2320, 7140, 21600, 65980, 200400, 610740, 1857520, 5656380, 17211840, 52396900, 159466800, 485403660, 1477389520, 4496881380, 13687155360, 41660429500, 126802853520, 385955704500, 1174746099760, 3575622750780
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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) = a(n-1) + 6*a(n-2) + a(n-3) - a(n-4) for n>5.
Empirical g.f.: 10*x*(1 + 9*x + 8*x^2 - 7*x^3 + x^4) / (1 - x - 6*x^2 - x^3 + x^4). - Colin Barker, Jun 25 2018
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EXAMPLE
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Some solutions for n=4:
..1..0..1..0....1..0..1..1....0..1..1..1....1..1..1..0....0..1..0..1
..0..1..0..0....1..0..1..1....1..0..1..0....1..0..1..0....1..0..1..1
..1..1..1..1....0..1..0..0....0..1..0..1....0..1..0..1....0..1..0..0
..1..0..1..0....0..1..0..0....1..0..1..1....1..1..1..1....1..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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