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A196918
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Number of n X 4 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, 4, 12, 37, 114, 335, 1003, 3051, 9290, 28268, 86013, 261786, 796995, 2426793, 7389825, 22503304, 68527674, 208684983, 635506294, 1935309489, 5893618625, 17947924171, 54657124744, 166448373086, 506888519813, 1543637889196
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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) = 4*a(n-1) -3*a(n-2) +a(n-3) -a(n-4) -a(n-5) -5*a(n-6) -8*a(n-7) -3*a(n-8) for n>9.
Empirical g.f.: x*(1 - x^2 - x^4 - 17*x^5 - 11*x^6 + 7*x^7 + 6*x^8) / (1 - 4*x + 3*x^2 - x^3 + x^4 + x^5 + 5*x^6 + 8*x^7 + 3*x^8). - Colin Barker, May 10 2018
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EXAMPLE
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Some solutions for n=5:
..0..0..0..0....0..2..2..0....0..0..0..0....0..2..2..2....0..0..0..0
..0..0..0..0....0..2..2..0....0..0..2..2....0..2..0..2....0..4..0..0
..2..2..0..0....0..0..0..0....0..0..2..2....0..2..0..2....0..0..2..2
..2..2..0..0....2..2..0..0....0..0..0..0....0..2..2..2....0..0..2..2
..0..0..0..0....2..2..0..0....0..0..0..0....0..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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