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A166914
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a(n) = 20*a(n-1) - 64*a(n-2) for n > 1; a(0) = 21, a(1) = 340.
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9
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21, 340, 5456, 87360, 1398016, 22369280, 357912576, 5726617600, 91625947136, 1466015416320, 23456247709696, 375299967549440, 6004799497568256, 96076792028200960, 1537228672719650816, 24595658764588154880
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OFFSET
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0,1
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COMMENTS
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Related to Reverse and Add trajectory of 318 in base 4: A075153(6*n+2) = 240*a(n).
lim_{n -> infinity} a(n)/a(n-1) = 16.
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LINKS
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FORMULA
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a(n) = (64*16^n - 4^n)/3.
G.f.: (21 - 80*x)/((1-4*x)*(1-16*x)).
a(n) = 20*a(n-1) - 64*a(n-2).
E.g.f.: (1/3)*(-exp(4*x) + 64*exp(16*x)). (End)
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MATHEMATICA
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CoefficientList[Series[(21-80x)/((1-4x)(1-16x)), {x, 0, 20}], x] (* or *) LinearRecurrence[{20, -64}, {21, 340}, 20] (* Harvey P. Dale, Feb 23 2011 & Mar 30 2012 *)
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PROG
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(PARI) {m=15; v=concat([21, 340], vector(m-2)); for(n=3, m, v[n]=20*v[n-1]-64*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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STATUS
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approved
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