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A208402
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Number of n X 2 0..3 arrays with new values 0..3 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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2, 15, 187, 2795, 43947, 700075, 11188907, 178973355, 2863377067, 45813246635, 733008800427, 11728128223915, 187650001250987, 3002399818689195, 48038396293720747, 768614337478306475, 12297829386768001707
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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) = 21*a(n-1) - 84*a(n-2) + 64*a(n-3).
G.f.: x*(2 - 27*x + 40*x^2) / ((1 - x)*(1 - 4*x)*(1 - 16*x)).
a(n) = (8 + 3*2^(1+2*n) + 16^n) / 24.
(End)
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EXAMPLE
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Some solutions for n=4:
..0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..0....0..1....0..0
..0..0....0..1....1..0....0..0....0..0....0..1....0..1....0..0....1..1....1..0
..1..1....0..0....0..2....0..1....1..2....1..0....0..0....1..0....0..0....2..0
..2..0....1..0....2..0....1..0....3..2....1..1....0..2....2..2....0..1....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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