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A251203
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Number of (n+1) X (1+1) 0..2 arrays with every 2 X 2 subblock summing to a nonzero multiple of 2.
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1
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40, 180, 816, 3728, 17152, 79424, 369920, 1731840, 8144896, 38458368, 182218752, 865931264, 4125491200, 19697254400, 94217240576, 451363012608, 2165141143552, 10397297147904, 49974875258880, 240389177999360, 1157058166521856
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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) = 8*a(n-1) - 12*a(n-2) - 16*a(n-3).
Empirical g.f.: 4*x*(10 - 35*x - 36*x^2) / ((1 - 4*x)*(1 - 4*x - 4*x^2)). - Colin Barker, Nov 26 2018
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EXAMPLE
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Some solutions for n=4:
..2..1....1..1....2..0....0..1....0..1....2..2....2..0....0..0....2..2....2..1
..1..0....1..1....0..2....1..0....0..1....1..1....0..0....2..2....2..2....1..0
..1..2....0..2....2..2....1..0....2..1....1..1....2..2....2..0....2..2....1..0
..1..0....1..1....2..2....1..0....2..1....1..1....0..2....2..0....2..2....2..1
..2..1....0..2....2..2....0..1....1..0....2..0....2..2....2..2....1..1....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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