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A195956
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Number of n X 2 0..4 arrays with each element equal to the number its horizontal and vertical neighbors unequal to itself.
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1
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1, 1, 6, 5, 5, 14, 21, 29, 54, 93, 149, 254, 437, 733, 1238, 2109, 3573, 6046, 10261, 17405, 29494, 50013, 84821, 143806, 243829, 413469, 701078, 1188733, 2015669, 3417822, 5795285, 9826621, 16662262, 28252829, 47906069, 81230590, 137736245
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OFFSET
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1,3
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) +3*a(n-3) -a(n-4) -2*a(n-6).
Empirical g.f.: x*(1 + 5*x^2 - 4*x^3 - 2*x^4 - 8*x^5) / ((1 - x)*(1 + x + x^2)*(1 - x - 2*x^3)). - Colin Barker, May 08 2018
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EXAMPLE
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All solutions for n=5:
..2..1....1..2....2..1....0..0....1..2
..3..1....1..3....1..1....0..0....1..1
..1..1....1..1....1..3....0..0....3..1
..1..3....3..1....1..1....0..0....1..1
..1..2....2..1....2..1....0..0....1..2
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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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