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A250871
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Number of (n+1) X (2+1) 0..3 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing x(i,j)+x(i-1,j) in the j direction.
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1
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288, 1456, 6812, 30360, 131068, 553736, 2304492, 9488920, 38773148, 157554216, 637620172, 2572727480, 10357724028, 41631485896, 167128007852, 670318814040, 2686696783708, 10763054076776, 43101021851532, 172550513476600
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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) = 10*a(n-1) - 35*a(n-2) + 50*a(n-3) - 24*a(n-4); a(n) = (472*4^n - 378*3^n + 54*2^n + 2)/3.
Empirical g.f.: 4*x*(72 - 356*x + 583*x^2 - 300*x^3) / ((1 - x)*(1 - 2*x)*(1 - 3*x)*(1 - 4*x)). - Colin Barker, Nov 22 2018
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EXAMPLE
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Some solutions for n=4:
..3..3..3....1..1..1....0..0..0....0..1..1....3..3..3....2..2..2....1..1..1
..1..1..1....2..2..2....0..1..1....0..1..1....1..1..2....0..0..0....1..1..1
..3..3..3....2..2..2....1..2..2....1..2..2....0..0..2....2..3..3....2..3..3
..1..1..1....1..1..3....0..1..2....1..2..2....1..1..3....1..2..2....0..1..1
..0..0..3....0..1..3....0..2..3....1..2..2....1..1..3....0..1..3....0..1..3
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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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