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A208690
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Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 1 and 1 0 1 vertically.
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1
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9, 81, 189, 927, 2889, 11727, 40581, 154359, 554733, 2062215, 7512453, 27700479, 101402109, 372809655, 1367107173, 5021003151, 18423673101, 67639822407, 248247487989, 911283026751, 3344800820445, 12277727839863, 45065827217925
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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) + 10*a(n-2) + 2*a(n-3) - 10*a(n-4).
Empirical g.f.: 9*x*(1 + 8*x + 2*x^2 - 10*x^3) / (1 - x - 10*x^2 - 2*x^3 + 10*x^4). - Colin Barker, Jul 05 2018
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EXAMPLE
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Some solutions for n=4:
..1..0..1..0....1..1..1..0....0..1..1..0....1..1..0..0....1..0..1..0
..1..1..1..0....1..0..1..1....0..1..0..0....1..1..1..0....1..0..1..0
..1..0..1..0....1..0..1..0....0..1..0..1....1..1..0..1....1..0..1..0
..1..0..1..0....1..0..1..0....0..1..0..0....0..1..0..0....0..1..1..0
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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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