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A230470
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Number of 2 X n 0..2 arrays x(i,j) with each element horizontally, diagonally or antidiagonally next to at least one element with value (x(i,j)+1) mod 3, and upper left element zero.
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1
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0, 0, 0, 36, 216, 1260, 6912, 38340, 213192, 1188252, 6624720, 36934452, 205906968, 1147892364, 6399246240, 35674383780, 198876914280, 1108695761532, 6180739391088, 34456287198996, 192086358160824, 1070839950246252
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OFFSET
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1,4
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LINKS
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FORMULA
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Empirical: a(n) = 6*a(n-1) - a(n-2) - 12*a(n-3) + 20*a(n-4) + 24*a(n-5).
Empirical g.f.: 36*x^3 / ((1 + x)*(1 - 7*x + 8*x^2 + 4*x^3 - 24*x^4)). - Colin Barker, Sep 21 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..2..0....0..0..1..0....0..1..0..0....0..1..1..0....0..2..2..0
..0..2..1..0....2..1..0..2....2..0..1..2....1..2..2..0....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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