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A207809
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Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 0 and 1 0 1 vertically.
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1
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10, 100, 370, 1970, 9040, 43990, 209050, 1002960, 4793390, 22944590, 109759520, 525189790, 2512723030, 12022412680, 57521607650, 275215898890, 1316784620900, 6300231318630, 30143802148430, 144224703156300, 690051081572450
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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) = 2*a(n-1) +13*a(n-2) +4*a(n-3) -12*a(n-4) +a(n-5) +a(n-6)
The empirical recursion is true: see link for Maple verification.
G.f.: (10*x+80*x^2+40*x^3-110*x^4+10*x^5+10*x^6)/(1-2*x-13*x^2-4*x^3+12*x^4-x^5-x^6). (End)
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EXAMPLE
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Some solutions for n=4:
..0..1..1..0....0..1..0..1....0..1..1..0....0..1..1..0....1..0..1..1
..1..1..0..0....1..0..1..1....0..1..1..1....0..1..0..1....0..1..0..0
..1..1..0..0....1..0..1..0....1..1..0..1....0..1..0..1....0..1..0..0
..0..1..1..1....1..1..0..0....1..1..0..1....1..1..0..1....1..0..1..0
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MAPLE
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f:= gfun:-rectoproc({a(n)=2*a(n-1) +13*a(n-2) +4*a(n-3) -12*a(n-4) +a(n-5) +a(n-6), seq(a(i)=[10, 100, 370, 1970, 9040, 43990][i], i=1..6)}, a(n), remember):
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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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