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A196917
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Number of n X 3 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 1,3,2,4,0 for x=0,1,2,3,4.
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1
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1, 3, 7, 12, 27, 58, 121, 257, 545, 1153, 2442, 5172, 10952, 23193, 49116, 104012, 220265, 466453, 987802, 2091857, 4429902, 9381153, 19866361, 42070767, 89092785, 188670778, 399545962, 846113942, 1791805877, 3794486938, 8035541856
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OFFSET
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1,2
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COMMENTS
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Every 0 is next to 0 1's, every 1 is next to 1 3's, every 2 is next to 2 2's, every 3 is next to 3 4's, every 4 is next to 4 0's.
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) +a(n-3) -a(n-4) for n>5.
Empirical g.f.: x*(1 + x + x^2 - 3*x^3 + x^4) / (1 - 2*x - x^3 + x^4). - Colin Barker, May 09 2018
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EXAMPLE
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Some solutions for n=4:
..0..0..0....0..2..2....0..0..0....0..0..0....0..0..0....0..0..0....0..0..0
..2..2..2....0..2..2....0..0..0....2..2..0....0..0..0....0..0..0....0..0..0
..2..0..2....0..0..0....0..2..2....2..2..0....2..2..0....0..4..0....0..0..0
..2..2..2....0..0..0....0..2..2....0..0..0....2..2..0....0..0..0....0..0..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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