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A208428
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Number of n X 2 0..2 arrays with new values 0..2 introduced in row major order and no element equal to any knight-move neighbor (colorings ignoring permutations of colors).
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3
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2, 14, 54, 216, 864, 3456, 13824, 55296, 221184, 884736, 3538944, 14155776, 56623104, 226492416, 905969664, 3623878656, 14495514624, 57982058496, 231928233984, 927712935936, 3710851743744, 14843406974976, 59373627899904
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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) = 4*a(n-1) for n>3.
G.f.: 2*x*(1 + 3*x - x^2) / (1 - 4*x).
a(n) = 27*2^(2*n - 5) for n>2.
(End)
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EXAMPLE
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Some solutions for n=4:
..0..0....0..0....0..0....0..1....0..0....0..0....0..1....0..0....0..0....0..0
..1..1....0..0....1..1....2..1....1..2....0..0....0..2....0..1....1..1....0..0
..1..1....1..2....1..2....2..1....1..2....1..2....2..2....2..1....2..1....1..1
..2..0....1..2....2..2....0..1....0..0....2..2....0..1....2..1....0..2....1..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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