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A167499
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a(n) = n*(n+3)/2 + 6.
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9
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6, 8, 11, 15, 20, 26, 33, 41, 50, 60, 71, 83, 96, 110, 125, 141, 158, 176, 195, 215, 236, 258, 281, 305, 330, 356, 383, 411, 440, 470, 501, 533, 566, 600, 635, 671, 708, 746, 785, 825, 866, 908, 951, 995, 1040, 1086, 1133, 1181, 1230, 1280, 1331, 1383, 1436, 1490
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OFFSET
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0,1
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COMMENTS
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LINKS
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FORMULA
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a(n) = n + a(n-1) + 1, with n > 1, a(1) = 8.
Sum_{n>=0} 1/a(n) = 2*Pi*tanh(Pi*sqrt(39)/2)/sqrt(39) - 1/5. - Amiram Eldar, Jan 17 2021
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MAPLE
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MATHEMATICA
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CoefficientList[Series[(6 - 10 x + 5 x^2) / (1 - x)^3, {x, 0, 60}], x] (* Vincenzo Librandi, Sep 16 2013 *)
LinearRecurrence[{3, -3, 1}, {6, 8, 11}, 60] (* Harvey P. Dale, Jun 21 2022 *)
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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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STATUS
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approved
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