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A268761
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Number of n X 3 binary arrays with some element plus some horizontally, vertically, diagonally or antidiagonally adjacent neighbor totalling two exactly once.
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1
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2, 15, 56, 223, 762, 2607, 8500, 27411, 86622, 270955, 838224, 2573015, 7841538, 23759463, 71619436, 214933915, 642504870, 1914023267, 5684288136, 16834582623, 49732758858, 146587890015, 431177727396, 1265883329827, 3710027613934
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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) = 4*a(n-1) + 2*a(n-2) - 16*a(n-3) - a(n-4) + 12*a(n-5) - 4*a(n-6).
Empirical g.f.: x*(2 + 7*x - 8*x^2 + x^3) / (1 - 2*x - 3*x^2 + 2*x^3)^2. - Colin Barker, Jan 14 2019
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EXAMPLE
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Some solutions for n=4:
..1..0..1. .0..1..1. .1..0..0. .1..0..1. .0..1..0. .1..1..0. .0..0..0
..0..0..1. .0..0..0. .0..0..0. .0..0..0. .0..0..1. .0..0..0. .0..0..0
..0..0..0. .0..0..0. .1..0..1. .0..1..0. .0..0..0. .0..0..0. .1..0..1
..0..0..0. .0..0..0. .0..0..1. .0..0..1. .0..0..1. .0..1..0. .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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