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A347108
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a(n) = Sum_{k=1..n} sigma(k)*sigma(2*k), where sigma(n) = A000203(n) is the sum of the divisors of n.
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0
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3, 24, 72, 177, 285, 621, 813, 1278, 1785, 2541, 2973, 4653, 5241, 6585, 8313, 10266, 11238, 14787, 15987, 19767, 22839, 25863, 27591, 35031, 37914, 42030, 46830, 53550, 56250, 68346, 71418, 79419, 86331, 93135, 100047, 117792, 122124, 130524, 139932, 156672
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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) ~ 2*zeta(3)*n^3.
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MATHEMATICA
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Accumulate[Table[DivisorSigma[1, k] * DivisorSigma[1, 2*k], {k, 1, 100}]]
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PROG
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(PARI) a(n) = sum(k=1, n, sigma(k)*sigma(2*k)); \\ Michel Marcus, Aug 18 2021
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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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