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A331131
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a(n) = Sum_{i=1..n} d(i)*d_3(i+1), where d(n) = A000005(n) and d_3(n) = A007425(n).
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1
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3, 9, 21, 30, 48, 60, 80, 104, 131, 143, 179, 197, 215, 251, 311, 326, 362, 380, 416, 470, 506, 518, 578, 626, 653, 693, 765, 783, 837, 861, 903, 957, 993, 1029, 1173, 1200, 1218, 1254, 1374, 1398, 1452, 1476, 1512, 1620, 1674, 1686, 1776, 1836, 1890, 1944, 2016, 2034, 2094, 2166, 2286, 2358, 2394
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OFFSET
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1,1
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REFERENCES
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József Sándor, Dragoslav S. Mitrinovic, Borislav Crstici, Handbook of Number Theory I, Springer Science & Business Media, 2005, page 62.
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LINKS
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FORMULA
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a(n) ~ c * n * log(n)^3, where c is a constant. - Amiram Eldar, Mar 05 2020
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MATHEMATICA
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f[p_, e_] := (e+1)*(e+2)/2; d3[1] = 1; d3[n_] := Times @@ f @@@ FactorInteger[n]; Accumulate @ Table[DivisorSigma[0, n] * d3[n+1], {n, 1, 60}] (* Amiram Eldar, Mar 05 2020 *)
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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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