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A208705
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Number of n X 4 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 right-upward antidiagonal neighbors.
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1
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8, 100, 1268, 16084, 204020, 2587924, 32826932, 416398420, 5281871732, 66998738836, 849856117940, 10780134577876, 136742325040628, 1734529687216660, 22001916633654068, 279086797488636244
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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) = 13*a(n-1) - 4*a(n-2).
G.f.: 4*x*(2 - x) / (1 - 13*x + 4*x^2).
a(n) = (2^(-1-n)*((13-3*sqrt(17))^n*(-1+sqrt(17)) + (1+sqrt(17))*(13+3*sqrt(17))^n)) / sqrt(17).
(End)
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EXAMPLE
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Some solutions for n=4:
..0..1..1..1....0..0..0..0....0..1..0..1....0..1..1..1....0..1..1..0
..0..0..1..1....0..1..1..0....0..0..1..0....1..0..0..0....0..0..1..0
..1..0..0..1....1..0..1..1....0..1..1..1....0..1..1..1....0..0..1..1
..0..1..1..1....1..1..0..1....1..0..1..1....1..0..0..0....1..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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