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A209649
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Number of n X 7 0..1 arrays avoiding 0 0 1 and 1 0 0 horizontally and 0 0 1 and 1 0 1 vertically.
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2
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35, 1225, 7210, 24990, 65765, 145775, 287140, 518700, 876855, 1406405, 2161390, 3205930, 4615065, 6475595, 8886920, 11961880, 15827595, 20626305, 26516210, 33672310, 42287245, 52572135, 64757420, 79093700, 95852575, 115327485
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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) = 7*n^5 + 70*n^4 + (35/3)*n^3 - (105/2)*n^2 - (7/6)*n.
G.f.: 35*x*(1 + x)*(1 + 28*x - 17*x^2) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.
(End)
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EXAMPLE
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Some solutions for n=4:
1 0 1 0 1 0 1 0 1 0 1 1 1 0 1 1 0 1 1 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 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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