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A253450
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Number of (n+1) X (2+1) 0..2 arrays with every 2 X 2 subblock diagonal minus antidiagonal sum nondecreasing horizontally and vertically.
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1
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414, 1975, 4782, 8554, 15220, 31630, 74324, 188438, 502364, 1387310, 3928484, 11324678, 33058604, 97351070, 288409844, 857948918, 2559291644, 7648770830, 22888110404, 68547933158, 205411009484, 615767454590, 1846371222164
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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) = 6*a(n-1) - 11*a(n-2) + 6*a(n-3) for n>9.
Empirical: a(n) = 529*3^(n-3) + 444*2^(n-1) + 3059 for n>6.
Empirical g.f.: x*(414 - 509*x - 2514*x^2 - 897*x^3 + 4648*x^4 + 5712*x^5 + 640*x^6 - 896*x^7 - 480*x^8) / ((1 - x)*(1 - 2*x)*(1 - 3*x)). - Colin Barker, Dec 13 2018
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EXAMPLE
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Some solutions for n=4:
..0..1..1....1..1..1....0..1..2....0..1..1....0..2..2....1..2..2....0..2..2
..2..0..0....1..0..0....0..0..0....2..2..2....1..2..2....1..1..0....1..2..2
..2..0..0....2..1..1....2..1..1....2..2..2....2..2..2....1..1..0....0..0..0
..2..0..0....1..0..0....1..0..0....0..0..0....0..0..0....2..2..1....0..0..0
..2..0..0....0..0..1....1..0..0....1..1..1....1..1..2....0..0..1....2..2..2
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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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