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A069914
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a(n) = Sum_{d|n} (d-1)*sigma(n/d).
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1
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0, 1, 2, 6, 4, 15, 6, 23, 16, 27, 10, 64, 12, 39, 42, 72, 16, 98, 18, 110, 60, 63, 22, 213, 48, 75, 84, 156, 28, 245, 30, 201, 96, 99, 102, 380, 36, 111, 114, 357, 40, 345, 42, 248, 248, 135, 46, 618, 96, 278, 150, 294, 52, 478, 162, 501, 168, 171, 58, 924, 60, 183
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OFFSET
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1,3
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LINKS
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FORMULA
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G.f.: Sum_{k>=1} sigma(k) * x^(2*k) / (1 - x^k)^2. - Ilya Gutkovskiy, Aug 19 2021
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MATHEMATICA
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Table[Plus @@ (DivisorSigma[1, ds = Divisors[n]]*(n/ds - 1)), {n, 62}] (* Ivan Neretin, May 17 2015 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, (d-1)*sigma(n/d)) \\ Michel Marcus, Jun 17 2013
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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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