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A270113
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Number of n X 3 0..7 arrays with some element plus some horizontally or vertically adjacent neighbor totaling seven exactly once.
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1
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112, 100800, 45440640, 16972694928, 5795977666752, 1877723928063648, 587581295287557312, 179399371883007424176, 53777749891851319065984, 15893068951375608455132544, 4643931350900992326932238336
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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) = 540*a(n-1) - 75994*a(n-2) + 835380*a(n-3) - 2393209*a(n-4) for n>5.
Empirical g.f.: 112*x*(1 + 360*x - 4286*x^2 + 12339*x^3 + 1225*x^4) / (1 - 270*x + 1547*x^2)^2. - Colin Barker, Jan 29 2019
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EXAMPLE
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Some solutions for n=2:
3 3 4 0 7 5 4 2 0 2 2 3 3 6 3 2 1 5 4 2 5
3 6 0 1 3 5 6 1 2 4 3 1 4 0 6 0 0 2 6 4 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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