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A250800
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Number of (3+1) X (n+1) 0..1 arrays with nondecreasing min(x(i,j),x(i,j-1)) in the i direction and nondecreasing absolute value of x(i,j)-x(i-1,j) in the j direction.
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1
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58, 180, 482, 1190, 2776, 6230, 13598, 29084, 61274, 127630, 263544, 540558, 1102982, 2241420, 4540290, 9173622, 18497880, 37239590, 74873806, 150386236, 301805898, 605284030, 1213273912, 2430926110, 4868936566, 9749335980
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 5*a(n-1) - 8*a(n-2) + 3*a(n-3) + 3*a(n-4) - 2*a(n-5).
Empirical g.f.: 2*x*(29 - 55*x + 23*x^2 + 23*x^3 - 16*x^4) / ((1 - x)^2*(1 - 2*x)*(1 - x - x^2)). - Colin Barker, Nov 20 2018
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EXAMPLE
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Some solutions for n=4:
..1..0..0..1..0....0..1..0..1..0....1..0..0..0..0....1..0..1..0..0
..0..1..1..0..1....0..1..0..1..0....1..0..0..0..1....1..0..0..1..1
..0..1..1..1..0....0..1..0..0..1....1..0..0..0..1....1..0..0..1..1
..0..1..1..1..1....0..1..0..0..0....1..0..0..0..0....1..0..0..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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