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A229514
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Number of n X 1 0..2 arrays of the median of the corresponding element, the element to the east and the element to the south in a larger (n+1) X 2 0..2 array without adjacent equal elements in the latter.
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1
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3, 7, 17, 39, 91, 211, 491, 1141, 2653, 6167, 14337, 33329, 77481, 180121, 418731, 973431, 2262953, 5260727, 12229707, 28430619, 66093171, 153647981, 357188221, 830361871, 1930357153, 4487535937, 10432255377, 24252051409, 56379179411
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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) = 2*a(n-1) + a(n-2) - a(n-3) + a(n-4).
Empirical g.f.: x*(3 + x + x^3) / ((1 + x)*(1 - 3*x + 2*x^2 - x^3)). - Colin Barker, Sep 18 2018
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EXAMPLE
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Some solutions for n=3:
..1....2....0....1....0....1....0....1....2....1....0....2....2....1....1....2
..0....0....2....2....2....1....1....2....0....1....1....1....1....0....1....1
..1....1....0....0....1....1....1....1....2....2....2....1....2....2....0....0
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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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