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A283078
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a(n) = sigma(7*n).
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13
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8, 24, 32, 56, 48, 96, 57, 120, 104, 144, 96, 224, 112, 171, 192, 248, 144, 312, 160, 336, 228, 288, 192, 480, 248, 336, 320, 399, 240, 576, 256, 504, 384, 432, 342, 728, 304, 480, 448, 720, 336, 684, 352, 672, 624, 576, 384, 992, 400, 744, 576, 784, 432, 960
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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) = (55*Pi^2/84) * n^2 + O(n*log(n)). (End)
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EXAMPLE
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For n = 3, the divisors of 3*7 are {1, 3, 7, 21}. Now, 1 + 3 + 7 + 21 = 32. So, a(3) = 32. - Indranil Ghosh, Feb 28 2017
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MATHEMATICA
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Table[DivisorSigma[1, 7n], {n, 1, 54}] (* Indranil Ghosh, Feb 28 2017 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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