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A156157
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a(n) = 6*a(n-1)-a(n-2) for n > 2; a(1) = 17, a(2) = 85.
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4
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17, 85, 493, 2873, 16745, 97597, 568837, 3315425, 19323713, 112626853, 656437405, 3825997577, 22299548057, 129971290765, 757528196533, 4415197888433, 25733659134065, 149986756915957, 874186882361677, 5095134537254105
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OFFSET
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1,1
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COMMENTS
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lim_{n -> infinity} a(n)/a(n-1) = 3+2*sqrt(2).
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LINKS
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FORMULA
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a(n) = ((2+sqrt(2))*(3-2*sqrt(2))^n+(2-sqrt(2))*(3+2*sqrt(2))^n)*17/4.
G.f.: 17*x*(1-x)/(1-6*x+x^2).
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PROG
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(PARI) {m=20; v=concat([17, 85], vector(m-2)); for(n=3, m, v[n]=6*v[n-1]-v[n-2]); v}
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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