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A166036
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a(n) = (4^n+8*(-5)^n)/9.
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6
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1, -4, 24, -104, 584, -2664, 14344, -67624, 354504, -1706984, 8797064, -42936744, 218878024, -1077612904, 5455173384, -27007431464, 136110899144, -676259528424, 3398477511304, -16923668079784
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = -a(n-1) + 20*a(n-2), a(0) = 1, a(1) = -4, for n>1.
a(n) = Sum_{k=0..n} A112555(n,k)*(-5)^k.
G.f.: (1-3x)/(1+x-20x^2).
E.g.f.: (1/9)*(exp(4*x) + 8*exp(-5*x)). - G. C. Greubel, Apr 24 2016
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MATHEMATICA
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Table[(4^n+8(-5)^n)/9, {n, 0, 30}] (* or *) LinearRecurrence[{-1, 20}, {1, -4}, 30] (* Harvey P. Dale, Mar 05 2016 *)
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PROG
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(PARI) vector(100, n, n--; (4^n+8*(-5)^n)/9) \\ Altug Alkan, Apr 24 2016
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CROSSREFS
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KEYWORD
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easy,sign
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AUTHOR
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STATUS
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approved
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