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A206866
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Number of n X 3 0..1 arrays avoiding 0 0 0 horizontally and 1 0 1 vertically.
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1
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7, 49, 211, 889, 3967, 17737, 78799, 350017, 1555843, 6915889, 30739447, 136629265, 607288711, 2699272273, 11997693379, 53327205481, 237028156975, 1053540057337, 4682762813455, 20813890672513, 92513343672307, 411202253906785
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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) = 4*a(n-1) + 8*a(n-3) + 4*a(n-4) - 2*a(n-5) - a(n-6).
Empirical g.f.: x*(7 + 21*x + 15*x^2 - 11*x^3 - 9*x^4 - x^5) / (1 - 4*x - 8*x^3 - 4*x^4 + 2*x^5 + x^6). - Colin Barker, Jun 17 2018
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EXAMPLE
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Some solutions for n=4:
0 1 0 1 1 1 0 1 1 1 1 0 0 1 0 0 1 1 0 0 1
1 0 1 1 1 0 1 1 0 0 0 1 1 0 0 0 1 1 0 0 1
0 0 1 1 0 0 1 1 0 0 0 1 1 0 1 0 1 1 1 1 1
0 1 0 1 0 1 1 0 1 1 0 0 1 1 0 0 1 1 0 0 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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