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A208873
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Number of 2 X n 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.
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1
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2, 12, 136, 1798, 24472, 334618, 4578580, 62655190, 857412640, 11733394642, 160567489036, 2197311225838, 30069453572632, 411490201499818, 5631102858140740, 77059719245016070, 1054535937228511120
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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) = 18*a(n-1) - 65*a(n-2) + 84*a(n-3) - 36*a(n-4) for n>5.
Empirical g.f.: 2*x*(1 - 12*x + 25*x^2 - 19*x^3 + 6*x^4) / ((1 - x)*(1 - 2*x)*(1 - 15*x + 18*x^2)). - Colin Barker, Jul 07 2018
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EXAMPLE
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Some solutions for n=4:
..0..0..1..0....0..0..0..0....0..0..1..0....0..0..0..0....0..1..1..0
..1..2..2..0....1..1..1..0....1..0..1..0....1..1..1..2....0..0..2..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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