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A269006
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Number of n X 3 binary arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two exactly once.
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1
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2, 8, 46, 224, 1066, 4952, 22654, 102416, 458674, 2038328, 8999374, 39512144, 172645498, 751190504, 3256354942, 14069557088, 60610482274, 260412843944, 1116181074286, 4773749750528, 20376053362762, 86813692172216
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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) = 10*a(n-1) - 31*a(n-2) + 24*a(n-3) + 21*a(n-4) - 18*a(n-5) - 9*a(n-6).
Empirical g.f.: 2*x*(1 - x)*(1 - 3*x)*(1 - 2*x + 3*x^2) / (1 - 5*x + 3*x^2 + 3*x^3)^2. - Colin Barker, Jan 18 2019
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EXAMPLE
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Some solutions for n=4:
..1..0..0. .1..0..1. .1..0..1. .0..1..1. .1..0..0. .0..1..1. .0..1..0
..1..0..0. .0..0..0. .0..0..0. .0..0..0. .0..1..0. .0..0..0. .1..0..0
..1..0..0. .0..0..0. .0..0..1. .0..0..1. .0..0..0. .0..0..0. .0..0..0
..0..1..0. .1..1..0. .0..1..0. .0..0..0. .1..0..0. .1..0..1. .1..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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