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A228501
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Number of n X 3 binary arrays with top left value 1 and no two ones adjacent horizontally, vertically, diagonally or antidiagonally.
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1
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2, 3, 12, 29, 88, 239, 684, 1909, 5392, 15143, 42644, 119933, 337512, 949535, 2671740, 7517061, 21150272, 59508247, 167433188, 471090573, 1325464216, 3729333775, 10492879052, 29522830997, 83065631600, 233713998087, 657579228980
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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) = 2*a(n-1) + 3*a(n-2) - 2*a(n-3).
Empirical g.f.: x*(2 - x) / (1 - 2*x - 3*x^2 + 2*x^3). - Colin Barker, Sep 11 2018
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EXAMPLE
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Some solutions for n=4:
..1..0..1....1..0..0....1..0..1....1..0..0....1..0..0....1..0..1....1..0..0
..0..0..0....0..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..0..1
..0..0..1....0..0..0....0..0..1....1..0..1....0..0..0....0..1..0....0..0..0
..0..0..0....1..0..0....1..0..0....0..0..0....0..0..1....0..0..0....0..0..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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