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A231390
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Number of (n+1) X (2+1) 0..2 arrays with no element unequal to a strict majority of its horizontal, diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order.
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1
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7, 8, 15, 20, 31, 52, 95, 180, 351, 692, 1375, 2740, 5471, 10932, 21855, 43700, 87391, 174772, 349535, 699060, 1398111, 2796212, 5592415, 11184820, 22369631, 44739252, 89478495, 178956980, 357913951, 715827892, 1431655775, 2863311540, 5726623071
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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) - 2*a(n-3) for n>5.
Empirical g.f.: x*(7 - 6*x - 8*x^2 - 4*x^3 - 8*x^4) / ((1 - x)*(1 + x)*(1 - 2*x)). - Colin Barker, Sep 28 2018
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EXAMPLE
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Some solutions for n=5:
..0..0..0....0..1..1....0..0..0....0..0..0....0..1..0....0..0..0....0..0..0
..1..1..1....1..0..1....0..0..0....1..1..1....1..0..1....0..0..0....0..0..0
..1..1..1....0..1..0....0..0..0....1..1..1....0..1..0....1..1..1....0..0..0
..2..2..2....1..0..1....0..0..0....1..1..1....1..0..1....1..1..1....1..1..1
..2..2..2....0..1..0....0..0..0....0..0..0....0..1..0....1..1..1....1..1..1
..1..1..1....0..0..1....1..1..1....0..0..0....1..0..1....0..0..0....0..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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