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A269215
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Number of 2 X n 0..3 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling three exactly once.
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2
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0, 96, 768, 6528, 49536, 360960, 2546304, 17563392, 119091072, 796813824, 5274483840, 34608512256, 225420724608, 1459142258688, 9394561013376, 60205610853120, 384263133750144, 2443755614295552, 15491594556534912
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 10*a(n-1) - 13*a(n-2) - 60*a(n-3) - 36*a(n-4).
G.f.: 96*x^2*(1 - x)^2 / ((1 + x)^2*(1 - 6*x)^2).
a(n) = 8*(175*6^n*n + 1008*n - 55*6^n - 288) / 1029 for n even.
a(n) = 8*(175*6^n*n - 1008*n - 55*6^n + 288) / 1029 for n odd.
(End)
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EXAMPLE
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Some solutions for n=4:
..3..1..1..0. .3..2..2..2. .0..1..1..1. .2..0..2..0. .3..3..3..3
..3..2..0..1. .2..0..2..0. .3..3..3..1. .1..2..2..2. .0..1..1..1
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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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