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A196294
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Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 3,0,1,4,2 for x=0,1,2,3,4.
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1
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3, 9, 20, 61, 187, 536, 1597, 4849, 14582, 44097, 134349, 409428, 1249517, 3822519, 11705002, 35866253, 109991817, 337493970, 1035913925, 3180693901, 9768462112, 30005758115, 92181317503, 283222651372, 870256732085, 2674196289015
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OFFSET
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1,1
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COMMENTS
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Every 0 is next to 0 3's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 4's, every 4 is next to 4 2's.
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) +4*a(n-2) +6*a(n-3) -9*a(n-4) -38*a(n-5) -32*a(n-6) -11*a(n-7) +6*a(n-8) +a(n-9).
Empirical g.f.: x*(1 + x)^2*(3 - 3*x - 7*x^2 - 16*x^3 - 3*x^4 + 15*x^5 + 2*x^6) / ((1 - x - 7*x^3 - x^4)*(1 - x - 5*x^2 - 4*x^3 - x^4 + x^5)). - Colin Barker, May 08 2018
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EXAMPLE
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Some solutions for n=4:
..0..0....1..0....1..2....1..0....0..0....2..1....0..1....1..0....0..1....1..0
..2..1....1..0....0..1....1..0....0..0....1..0....0..2....2..0....0..2....2..1
..1..1....1..1....0..1....1..0....0..0....1..1....2..1....1..0....0..1....2..1
..0..0....0..1....1..2....2..1....1..1....0..1....1..0....1..0....1..2....1..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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