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A235653
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Number of (n+1) X (1+1) 0..1 arrays with the difference of the upper median and minimum value of each 2 X 2 subblock in lexicographically nondecreasing order rowwise and columnwise.
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2
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16, 52, 160, 476, 1392, 4020, 11520, 32828, 93200, 263892, 745824, 2105116, 5936304, 16729076, 47122368, 132690428, 373551952, 1051454740, 2959233056, 8327823580, 23434631152, 65942655540, 185550334592, 522092927932, 1469018657424
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 4*a(n-1) - a(n-2) - 8*a(n-3) + 4*a(n-4).
Empirical g.f.: 4*x*(4 - 3*x - 8*x^2 + 4*x^3) / ((1 - 2*x)*(1 - 2*x - 3*x^2 + 2*x^3)). - Colin Barker, Mar 19 2018
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EXAMPLE
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Some solutions for n=5:
..0..1....0..1....0..0....0..1....0..1....0..1....0..1....0..1....1..0....1..1
..0..0....0..0....0..0....0..0....1..1....0..0....1..0....0..0....1..0....0..1
..1..0....0..1....1..0....1..0....0..1....1..0....0..1....0..1....0..1....1..1
..0..1....0..0....0..1....1..0....0..1....1..1....0..1....1..0....1..0....0..0
..1..0....1..0....1..0....1..1....1..1....0..0....0..1....0..1....0..1....1..1
..1..0....1..1....1..0....1..0....1..0....1..1....0..1....1..1....1..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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