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A269054
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Number of 3 X n 0..2 arrays with some element plus some horizontally, diagonally or antidiagonally adjacent neighbor totalling two not more than once.
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1
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27, 174, 594, 3078, 13140, 58752, 253416, 1090344, 4637904, 19604352, 82332384, 343986912, 1430547456, 5925418752, 24456120000, 100618925568, 412797979584, 1689208728576, 6896384506176, 28095875422848, 114241910041536
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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) = 6*a(n-1) - a(n-2) - 28*a(n-3) - 4*a(n-4) + 16*a(n-5) - 4*a(n-6) for n>8.
Empirical g.f.: 3*x*(9 + 4*x - 141*x^2 + 148*x^3 + 82*x^4 - 38*x^5 - 24*x^6 + 8*x^7) / (1 - 3*x - 4*x^2 + 2*x^3)^2. - Colin Barker, Jan 18 2019
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EXAMPLE
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Some solutions for n=4:
..2..2..1..1. .0..1..2..2. .0..1..0..1. .2..2..1..2. .1..1..2..1
..2..2..2..2. .0..1..0..1. .0..0..0..1. .2..2..1..2. .2..2..2..2
..1..2..1..2. .2..1..2..1. .1..1..0..0. .2..2..2..1. .1..2..1..2
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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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