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A168419
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a(n) = 9*floor(n/2).
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1
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0, 9, 9, 18, 18, 27, 27, 36, 36, 45, 45, 54, 54, 63, 63, 72, 72, 81, 81, 90, 90, 99, 99, 108, 108, 117, 117, 126, 126, 135, 135, 144, 144, 153, 153, 162, 162, 171, 171, 180, 180, 189, 189, 198, 198, 207, 207, 216, 216, 225, 225, 234, 234, 243, 243, 252, 252, 261
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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) = 9*n - a(n-1) - 9, with n>1, a(1)=0.
E.g.f.: (9/4)*(1 + (2*x - 1)*exp(2*x))*exp(-x). - G. C. Greubel, Jul 22 2016
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MATHEMATICA
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Table[9 Floor[n/2], {n, 70}] (* or *) CoefficientList[Series[9 x/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 19 2013 *)
LinearRecurrence[{1, 1, -1}, {0, 9, 9}, 60] (* Harvey P. Dale, Apr 21 2019 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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