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A232935
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Number of n X 2 0..2 arrays with no element x(i,j) adjacent to value 2-x(i,j) horizontally, vertically or antidiagonally.
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1
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6, 12, 26, 56, 120, 258, 554, 1190, 2556, 5490, 11792, 25328, 54402, 116850, 250982, 539084, 1157898, 2487048, 5341928, 11473922, 24644826, 52934598, 113698172, 244212194, 524543136, 1126665696, 2419964162, 5197838690, 11164432710
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = a(n-1) + 2*a(n-2) + a(n-3).
Empirical g.f.: 2*x*(3 + 3*x + x^2) / (1 - x - 2*x^2 - x^3). - Colin Barker, Oct 06 2018
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EXAMPLE
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Some solutions for n=5:
..2..1....0..0....0..1....0..0....1..2....0..1....1..0....2..2....0..1....0..0
..2..2....0..1....0..0....0..1....2..1....0..0....0..1....2..2....0..0....1..0
..1..2....0..0....0..1....0..0....2..2....1..0....0..0....2..1....1..0....0..0
..2..1....0..0....0..0....1..0....2..2....0..0....1..0....2..2....0..1....0..0
..2..2....0..1....1..0....0..1....2..1....0..1....0..1....2..2....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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