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A197497
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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 2,3,1,1,0 for x=0,1,2,3,4.
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1
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1, 1, 9, 9, 19, 45, 73, 147, 291, 539, 1051, 2025, 3863, 7451, 14313, 27465, 52817, 101457, 194891, 374517, 719505, 1382347, 2655995, 5102835, 9804019, 18836497, 36190191, 69531891, 133591057, 256666833, 493131481, 947448537, 1820322627
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OFFSET
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1,3
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COMMENTS
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Every 0 is next to 0 2's, every 1 is next to 1 3's, every 2 is next to 2 1's, every 3 is next to 3 1'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) = a(n-1) +a(n-2) +2*a(n-3) -a(n-4).
Empirical g.f.: x*(1 + 7*x^2 - 3*x^3) / (1 - x - x^2 - 2*x^3 + x^4). - Colin Barker, May 12 2018
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EXAMPLE
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All solutions for n=4:
..0..0....2..1....0..0....0..0....1..0....0..0....1..2....0..1....0..0
..0..1....1..3....0..1....0..0....3..1....1..0....3..1....1..3....1..0
..1..3....0..1....1..3....0..0....1..0....3..1....1..0....0..1....3..1
..2..1....0..0....0..1....0..0....0..0....1..2....0..0....0..0....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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