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A268966
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Number of n X 3 0..2 arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two not more than once.
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1
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24, 240, 2016, 15552, 114048, 808704, 5598720, 38071296, 255301632, 1693052928, 11125776384, 72559411200, 470184984576, 3030081011712, 19434312695808, 124128835928064, 789910774087680, 5010291195641856, 31686706480545792
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OFFSET
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1,1
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LINKS
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R. H. Hardin, Table of n, a(n) for n = 1..210
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FORMULA
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Empirical: a(n) = 12*a(n-1) - 36*a(n-2).
Conjectures from Colin Barker, Jan 17 2019: (Start)
G.f.: 24*x*(1 - 2*x) / (1 - 6*x)^2.
a(n) = 2^(n+2) * 3^(n-1) * (2*n+1).
(End)
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EXAMPLE
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Some solutions for n=4:
..1..0..0. .0..1..2. .0..2..2. .2..2..2. .0..0..0. .1..2..1. .1..2..2
..1..1..2. .2..2..2. .1..2..2. .1..2..2. .0..1..0. .2..1..0. .0..1..0
..2..2..2. .1..2..2. .2..2..2. .1..0..1. .2..0..1. .0..0..1. .0..0..1
..2..2..2. .2..1..0. .2..2..2. .1..0..0. .1..0..1. .1..2..1. .0..0..0
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CROSSREFS
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Column 3 of A268971.
Sequence in context: A000919 A353665 A353775 * A014340 A052753 A353358
Adjacent sequences: A268963 A268964 A268965 * A268967 A268968 A268969
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KEYWORD
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nonn
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AUTHOR
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R. H. Hardin, Feb 16 2016
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STATUS
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approved
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