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A208264
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Number of n X 3 0..1 arrays with new values 0..1 introduced in row major order and no element equal to more than two of its immediate leftward or upward or left-upward diagonal neighbors.
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1
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4, 25, 161, 1033, 6631, 42563, 273205, 1753657, 11256431, 72253147, 463780861, 2976931745, 19108426759, 122653794067, 787294181189, 5053509615817, 32437632650335, 208211736387083, 1336476297041869, 8578617726111793
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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) = 6*a(n-1) + 3*a(n-2) - 2*a(n-3).
Empirical g.f.: x*(4 + x - x^2) / (1 - 6*x - 3*x^2 + 2*x^3). - Colin Barker, Jun 29 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..0....0..0..1....0..1..1....0..1..1....0..0..0....0..0..0....0..0..1
..0..0..0....0..1..0....1..1..0....0..1..0....1..0..1....0..1..1....0..1..1
..1..1..1....1..1..1....0..1..0....0..1..1....1..0..1....1..0..1....1..0..0
..1..0..0....0..0..0....0..1..0....0..1..0....1..0..1....0..1..0....1..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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