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A208380
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Number of 4 X n 0..1 arrays avoiding 0 0 0 and 1 1 1 horizontally and 0 0 1 and 1 0 1 vertically.
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1
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8, 64, 108, 420, 1344, 4212, 13860, 44880, 144540, 468852, 1517184, 4906980, 15883764, 51401040, 166325292, 538259268, 1741843392, 5636673684, 18240740100, 59028275280, 191019298428, 618151779156, 2000381177088, 6473368570500
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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) + 4*a(n-2) + 9*a(n-3) + 5*a(n-4) - 2*a(n-5) + 4*a(n-6) for n>8.
Empirical g.f.: 4*x*(2 + 14*x + 3*x^2 - 4*x^3 - 31*x^4 - 22*x^5 + 12*x^6 - 16*x^7) / ((1 - 2*x - 4*x^2)*(1 + x + 2*x^2 - x^3 + x^4)). - Colin Barker, Jul 02 2018
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EXAMPLE
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Some solutions for n=4:
..1..0..1..1....1..0..0..1....1..0..0..1....1..1..0..1....1..0..0..1
..1..0..0..1....0..1..0..1....1..1..0..0....1..1..0..1....0..1..1..0
..1..0..0..1....0..1..0..0....1..1..0..0....0..1..0..0....0..0..1..0
..1..0..0..1....0..1..0..0....1..1..0..0....0..1..0..0....0..0..1..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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