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A168332
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a(n) = 6 + 7 * floor((n-1)/2).
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2
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6, 6, 13, 13, 20, 20, 27, 27, 34, 34, 41, 41, 48, 48, 55, 55, 62, 62, 69, 69, 76, 76, 83, 83, 90, 90, 97, 97, 104, 104, 111, 111, 118, 118, 125, 125, 132, 132, 139, 139, 146, 146, 153, 153, 160, 160, 167, 167, 174, 174, 181, 181, 188, 188, 195, 195, 202, 202, 209
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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) = 7*n - a(n-1) - 2, with n>1, a(1)=6.
E.g.f.: (1/2)*(2 + (7*x - 2)*cosh(x) + (7*x + 5)*sinh(x)). - G. C. Greubel, Jul 18 2016
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MATHEMATICA
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Table[6 + 7 Floor[(n - 1)/2], {n, 60}] (* Bruno Berselli, Sep 17 2013 *)
CoefficientList[Series[(6 + x^2)/((1 + x) (x - 1)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 17 2013 *)
LinearRecurrence[{1, 1, -1}, {6, 6, 13}, 60] (* or *) With[{c=NestList[ #+7&, 6, 30]}, Riffle[c, c]] (* Harvey P. Dale, Aug 29 2015 *)
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PROG
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(Magma) [n eq 1 select 6 else 7*n-Self(n-1)-2: n in [1..70]]; // Vincenzo Librandi, Sep 17 2013
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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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