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A204375
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Number of (n+2) X 4 0..1 arrays with every 3 X 3 subblock having three equal elements in a row horizontally, vertically or nw-to-se diagonally exactly three ways, and new values 0..1 introduced in row major order.
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1
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51, 48, 54, 63, 88, 128, 193, 300, 470, 747, 1196, 1920, 3093, 4992, 8062, 13031, 21072, 34080, 55129, 89188, 144294, 233459, 377732, 611168, 988877, 1600024, 2588878, 4188879, 6777736, 10966592, 17744305, 28710876, 46455158, 75166011, 121621148
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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) = a(n-1) +a(n-2) +a(n-3) -a(n-4) -a(n-5) for n>8.
Empirical g.f.: x*(51 - 3*x - 45*x^2 - 90*x^3 - 26*x^4 + 22*x^5 + 16*x^6 + 8*x^7) / ((1 - x)*(1 - x - x^2)*(1 + x + x^2)). - Colin Barker, Jun 07 2018
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EXAMPLE
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Some solutions for n=3:
..0..1..1..1....0..0..0..0....0..0..0..1....0..0..1..0....0..0..0..1
..0..0..1..1....0..0..0..0....1..1..0..1....0..0..1..0....1..1..1..1
..0..0..0..1....1..1..1..1....0..0..0..0....0..0..1..0....1..1..1..1
..1..0..0..0....0..0..0..0....0..0..0..0....0..0..1..0....0..0..0..0
..0..1..0..0....0..0..0..0....1..1..1..1....0..0..1..0....1..1..1..1
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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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