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A168457
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a(n) = (10*n + 5*(-1)^n - 1)/2.
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3
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2, 12, 12, 22, 22, 32, 32, 42, 42, 52, 52, 62, 62, 72, 72, 82, 82, 92, 92, 102, 102, 112, 112, 122, 122, 132, 132, 142, 142, 152, 152, 162, 162, 172, 172, 182, 182, 192, 192, 202, 202, 212, 212, 222, 222, 232, 232, 242, 242, 252, 252, 262, 262, 272, 272, 282
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n) = 10*n - a(n-1) - 6 for n>1, a(1)=2.
G.f.: 2*x*(1 + 5*x - x^2)/((1+x)*(1-x)^2).
a(n) = a(n-1) +a(n-2) -a(n-3). (End)
E.g.f.: (1/2)*(5 - 4*exp(x) + (10*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 22 2016
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MATHEMATICA
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Table[5 n + 5 (-1)^n/2 - 1/2, {n, 60}] (* Bruno Berselli, Sep 16 2013 *)
Table[2 + 10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[2 (1 + 5 x - x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy,less
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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