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A168459
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a(n) = (10*n + 5*(-1)^n - 3)/2.
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3
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1, 11, 11, 21, 21, 31, 31, 41, 41, 51, 51, 61, 61, 71, 71, 81, 81, 91, 91, 101, 101, 111, 111, 121, 121, 131, 131, 141, 141, 151, 151, 161, 161, 171, 171, 181, 181, 191, 191, 201, 201, 211, 211, 221, 221, 231, 231, 241, 241, 251, 251, 261, 261, 271, 271, 281
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 10*n - a(n-1) - 8 with n>1, a(1)=1.
G.f.: x*(1 + 10*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 - 2*exp(x) + (10*x - 3)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 23 2016
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MATHEMATICA
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Table[5 n + 5 (-1)^n/2 - 3/2, {n, 60}] (* Bruno Berselli, Sep 16 2013 *)
Table[1 + 10 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[(1 + 10 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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