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A119032
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a(n+2)=18a(n+1)-a(n)+8.
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3
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0, 9, 170, 3059, 54900, 985149, 17677790, 317215079, 5692193640, 102142270449, 1832868674450, 32889493869659, 590178020979420, 10590314883759909, 190035489886698950, 3410048503076821199, 61190837565496082640
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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a(n+1) = 9*a(n+1)+4+(80*a(n)^2+80*a(n)+25)^0.5.
G.f.: f(z)=a(0)+a(1)*z+a(2)*z^2+...=(9*z-z^2)/((1-z)*(1-18*z+z^2))
a(n) = ((sqrt(5)+2)/8)*(9+4*sqrt(5))^n+((-sqrt(5)+2)/8)*(9-4*sqrt(5))^n-0.5 [From Richard Choulet, Nov 26 2008]
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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