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A269209
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Number of n X 3 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three exactly once.
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1
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24, 768, 18048, 361728, 6712704, 118872576, 2039727744, 34214296320, 564168820608, 9179147971584, 147751571802240, 2357407757843712, 37337046775523712, 587670598254177792, 9200252201653201536
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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) = 30*a(n-1) - 237*a(n-2) + 180*a(n-3) - 36*a(n-4) for n>5.
Empirical g.f.: 24*x*(1 + 2*x + 29*x^2 - 84*x^3 + 36*x^4) / (1 - 15*x + 6*x^2)^2. - Colin Barker, Jan 20 2019
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EXAMPLE
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Some solutions for n=3:
..0..0..0. .2..0..0. .3..2..3. .1..3..1. .2..0..0. .2..3..3. .2..3..3
..0..0..2. .2..2..2. .2..2..3. .1..1..1. .1..2..2. .1..3..3. .3..1..3
..1..2..2. .0..3..2. .3..3..0. .3..3..0. .3..3..2. .2..0..2. .0..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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