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A197102
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Half the number of n X 1 0..3 arrays with no element equal to the average of its horizontal and vertical neighbors.
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1
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2, 6, 16, 61, 212, 753, 2661, 9415, 33302, 117802, 416703, 1474018, 5214089, 18443961, 65242401, 230783990, 816359440, 2887733833, 10214871388, 36133384697, 127815754113, 452126672783, 1599321849338, 5657331300590
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 2*a(n-1) +5*a(n-2) +3*a(n-3) -4*a(n-4) -4*a(n-5) for n>6.
Empirical g.f.: x*(2 + 2*x - 6*x^2 - 7*x^3 + 8*x^5) / (1 - 2*x - 5*x^2 - 3*x^3 + 4*x^4 + 4*x^5). - Colin Barker, May 11 2018
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EXAMPLE
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Some solutions for 4 X 4:
..0....0....0....0....1....1....0....1....1....1....1....0....0....0....1....1
..1....1....3....3....0....0....3....3....0....0....2....1....3....1....0....2
..1....0....3....2....3....0....3....0....0....1....0....1....0....0....3....0
..0....3....1....0....2....2....2....2....1....0....2....3....1....2....0....1
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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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