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A250733
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Number of (4+1) X (n+1) 0..1 arrays with nondecreasing 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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58, 144, 365, 885, 2092, 4889, 11377, 26419, 61330, 142336, 330417, 767047, 1781019, 4135537, 9603827, 22303104, 51797791, 120298572, 279397140, 648909915, 1507137312, 3500429630, 8130041844, 18882699707, 43856786967, 101861340070
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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) = 4*a(n-1) - a(n-2) - 13*a(n-3) + 15*a(n-4) + 3*a(n-5) - 11*a(n-6) + 4*a(n-7) for n>9.
Empirical g.f.: x*(58 - 88*x - 153*x^2 + 323*x^3 - 81*x^4 - 183*x^5 + 149*x^6 - 22*x^7 - 8*x^8) / ((1 - x)^2*(1 - 2*x - 4*x^2 + 7*x^3 + 3*x^4 - 4*x^5)). - Colin Barker, Nov 16 2018
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EXAMPLE
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Some solutions for n=4:
..0..0..0..0..0....0..0..0..0..1....0..0..0..0..0....0..0..0..0..0
..0..0..0..0..0....0..0..0..0..1....0..0..0..0..0....0..0..0..0..0
..0..0..0..0..0....0..0..0..0..1....0..0..0..0..1....0..0..0..1..1
..1..0..0..0..1....1..0..1..1..1....0..0..0..1..0....0..0..1..1..1
..0..1..1..1..0....0..1..1..1..1....0..0..1..0..1....0..1..1..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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