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A210088
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Number of (n+1) X 2 0..2 arrays containing all values 0..2 with every 2 X 2 subblock having one or two distinct values, and new values 0..2 introduced in row major order.
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1
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0, 9, 90, 657, 4230, 25533, 148410, 842265, 4704750, 25994709, 142528770, 777216177, 4221470070, 22863109293, 123563792970, 666766408905, 3593844532350, 19354295087109, 104165322930450, 560359838547297
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 10*a(n-1) - 27*a(n-2) + 10*a(n-3) + 8*a(n-4).
Empirical g.f.: 9*x^2 / ((1 - x)*(1 - 4*x)*(1 - 5*x - 2*x^2)). - Colin Barker, Jul 14 2018
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EXAMPLE
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Some solutions for n=4:
..0..0....0..0....0..1....0..0....0..1....0..0....0..0....0..1....0..0....0..1
..1..0....0..0....0..0....1..1....1..1....0..1....0..1....1..1....0..1....0..1
..1..0....0..0....1..0....1..0....0..0....0..0....0..0....1..0....0..0....0..0
..0..0....1..1....0..0....1..1....1..1....0..2....2..0....1..1....0..2....2..0
..0..2....1..2....0..2....1..2....1..2....2..0....0..0....2..1....0..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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