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A069440
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Half the number of n X 2 binary arrays with no path of adjacent 1's or adjacent 0's from top row to bottom row.
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0
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0, 2, 16, 88, 414, 1810, 7616, 31376, 127710, 516170, 2077552, 8341288, 33440190, 133941922, 536205056, 2145876128, 8586053694, 34350369050, 137416333936, 549701205496, 2198891419230, 8795774741170, 35183603690432, 140735633277488, 562945474867230
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 7*a(n-1) - 13*a(n-2) + 3*a(n-3) + 4*a(n-4).
G.f.: 2*x^2*(1+x+x^2)/((1-x)*(1-4*x)*(1-2*x-x^2)). (End)
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CROSSREFS
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KEYWORD
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nonn,easy,changed
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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