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A229314
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Number of n X 1 0..3 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..3 array without adjacent equal elements in the latter.
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1
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4, 14, 50, 176, 622, 2196, 7756, 27390, 96730, 341606, 1206400, 4260462, 15046040, 53135856, 187651986, 662702554, 2340367858, 8265128408, 29188722358, 103081461140, 364037435444, 1285616763070, 4540221143674, 16034022443998
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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) + 2*a(n-2) - a(n-3) + 2*a(n-4).
Empirical g.f.: 2*x*(1 + x)*(2 - x + x^2) / (1 - 3*x - 2*x^2 + x^3 - 2*x^4). - Colin Barker, Sep 14 2018
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EXAMPLE
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Some solutions for n=3:
..1....3....2....0....0....1....2....2....0....1....3....3....2....2....2....1
..3....0....0....2....1....1....2....3....3....3....1....2....1....1....3....3
..1....2....3....2....0....1....2....2....2....0....1....0....1....0....1....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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