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A250576
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Number of (n+1) X (1+1) 0..1 arrays with nondecreasing max(x(i,j),x(i,j-1)) in the i direction and nondecreasing min(x(i,j),x(i-1,j)) in the j direction.
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1
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10, 24, 55, 125, 282, 635, 1428, 3210, 7214, 16211, 36427, 81852, 183921, 413268, 928606, 2086560, 4688459, 10534873, 23671646, 53189707, 119516188, 268550438, 603427358, 1355888967, 3046654855, 6845771320, 15382308529, 34563733524
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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) = 3*a(n-1) - a(n-2) - 2*a(n-3) +a(n-4).
Empirical g.f.: x*(10 - 6*x - 7*x^2 + 4*x^3) / ((1 - x)*(1 - 2*x - x^2 + x^3)). - Colin Barker, Nov 15 2018
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EXAMPLE
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Some solutions for n=6:
..0..0....1..1....1..1....0..1....0..0....1..1....0..0....0..0....0..0....1..1
..1..1....0..1....0..1....1..1....1..1....0..1....0..0....0..0....0..0....0..1
..1..1....1..0....0..1....1..1....1..1....1..1....1..1....1..0....0..0....0..1
..0..1....0..1....1..1....0..1....1..1....0..1....0..1....0..1....1..1....1..1
..0..1....1..0....1..1....0..1....0..1....0..1....1..0....1..1....1..1....1..1
..0..1....0..1....0..1....1..1....1..0....0..1....0..1....1..1....0..1....1..1
..1..1....1..0....1..0....1..1....0..1....1..0....1..1....0..1....1..0....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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