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A209220
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Number of n X 4 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 1 0 and 1 1 1 vertically.
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1
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9, 81, 100, 196, 324, 576, 1024, 1764, 3136, 5476, 9604, 16900, 29584, 51984, 91204, 160000, 280900, 492804, 864900, 1517824, 2663424, 4674244, 8202496, 14394436, 25260676, 44328964, 77792400, 136515856, 239568484, 420414016, 737774244
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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) - a(n-6) for n > 8.
Empirical g.f.: x*(9 + 72*x + 10*x^2 + 6*x^3 - 44*x^4 + 28*x^5 - 44*x^6 + 17*x^7) / ((1 - 2*x + x^2 - x^3)*(1 + x - x^3)). - Colin Barker, Jul 08 2018
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EXAMPLE
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Some solutions for n=4:
0 1 1 1 0 0 1 1 0 1 1 1 1 0 0 1 0 0 1 1
0 1 1 0 1 1 0 0 0 0 1 1 0 1 1 0 1 1 1 0
1 0 0 1 1 1 1 0 1 1 0 0 1 1 1 1 1 1 0 0
1 1 1 1 0 0 1 1 1 1 0 0 1 0 0 1 0 0 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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