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A250798
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Number of (1+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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10, 24, 54, 118, 252, 530, 1102, 2272, 4654, 9486, 19260, 38986, 78726, 158672, 319318, 641830, 1288828, 2586018, 5185566, 10393024, 20821470, 41700254, 83493244, 167136538, 334515862, 669424560, 1339484742, 2679997942, 5361659964
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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).
Empirical g.f.: 2*x*(5 - 3*x - 4*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:
..0..1..0..0..0....0..1..0..1..0....0..1..0..0..1....1..0..1..0..0
..1..0..1..1..1....1..0..1..0..1....0..1..0..0..0....1..0..1..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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