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A210397
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Number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having one or three distinct values, and new values 0..3 introduced in row major order.
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1
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7, 59, 549, 5167, 48689, 458859, 4324477, 40755719, 384099369, 3619917187, 34115652149, 321520538079, 3030147451297, 28557409213979, 269137272730989, 2536465091434807, 23904734913837209, 225288474590274099
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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) = 10*a(n-1) - 5*a(n-2) - 4*a(n-3).
Empirical g.f.: x*(1 - 2*x)*(7 + 3*x) / ((1 - x)*(1 - 9*x - 4*x^2)). - Colin Barker, Jul 15 2018
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EXAMPLE
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Some solutions for n=4:
..0..0....0..0....0..0....0..0....0..1....0..1....0..0....0..0....0..1....0..0
..0..0....0..0....0..0....1..2....0..2....2..2....0..0....0..0....0..2....0..0
..0..0....0..0....0..0....0..1....0..1....1..0....0..0....0..0....3..3....1..2
..1..2....0..0....1..2....1..3....1..2....0..3....1..2....0..0....3..3....2..0
..1..0....1..2....2..0....3..0....2..3....0..1....3..3....0..0....1..2....2..3
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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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