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A196701
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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 3,1,0,4,2 for x=0,1,2,3,4.
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1
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2, 11, 38, 136, 488, 1744, 6208, 22202, 79292, 282984, 1010760, 3609442, 12887556, 46021868, 164340008, 586827146, 2095503116, 7482801488, 26720080488, 95414259450, 340712829860, 1216643200052, 4344485254120, 15513628195858
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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 zero 3's, every 1 is next to one 1's, every 2 is next to two 0's, every 3 is next to three 4's, every 4 is next to four 2's.
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) +4*a(n-2) +16*a(n-3) +9*a(n-4) -a(n-5) +2*a(n-6) +2*a(n-7) for n>8.
Empirical g.f.: x*(2 + 9*x + 19*x^2 + 22*x^3 + 6*x^4 + 7*x^5 + x^6 - 2*x^7) / (1 - x - 4*x^2 - 16*x^3 - 9*x^4 + x^5 - 2*x^6 - 2*x^7). - Colin Barker, May 09 2018
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EXAMPLE
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Some solutions for n=4:
..0..2....0..0....0..0....0..2....1..1....0..0....0..1....0..1....2..0....0..0
..0..0....2..1....0..2....2..0....0..0....2..0....0..1....0..1....0..0....0..2
..0..0....0..1....0..1....1..2....1..0....2..0....0..2....0..0....2..2....0..2
..0..2....0..0....0..1....1..0....1..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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