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A144613
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a(n) = sigma(3*n) = A000203(3*n).
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16
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4, 12, 13, 28, 24, 39, 32, 60, 40, 72, 48, 91, 56, 96, 78, 124, 72, 120, 80, 168, 104, 144, 96, 195, 124, 168, 121, 224, 120, 234, 128, 252, 156, 216, 192, 280, 152, 240, 182, 360, 168, 312, 176, 336, 240, 288, 192, 403, 228, 372, 234, 392, 216, 363, 288, 480, 260, 360
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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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Sum_{k=1..n} a(k) = (11*Pi^2/36) * n^2 + O(n*log(n)). - Amiram Eldar, Dec 16 2022
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MATHEMATICA
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a[n_] := DivisorSigma[1, 3*n]; Array[a, 60] (* Amiram Eldar, Dec 16 2022 *)
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PROG
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(PARI) vector(66, n, sigma(3*n, 1)) \\ Joerg Arndt, Jul 30 2011
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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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Zero removed and offset corrected by Seiichi Manyama, Feb 28 2017
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STATUS
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approved
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