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A321563
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a(n) = Sum_{d divides n} (-1)^(d + n/d) * d^7.
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3
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1, -129, 2188, -16257, 78126, -282252, 823544, -2080641, 4785157, -10078254, 19487172, -35570316, 62748518, -106237176, 170939688, -266321793, 410338674, -617285253, 893871740, -1270094382, 1801914272, -2513845188, 3404825448, -4552442508
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f.: Sum_{k>=1} (-1)^(k+1)*k^7*x^k/(1 + x^k). - Ilya Gutkovskiy, Dec 22 2018
Multiplicative with a(2^e) = -3*(21*2^(7*e+1) + 85)/127, and a(p^e) = (p^(7*e+7) - 1)/(p^7 - 1) for p > 2. - Amiram Eldar, Nov 22 2022
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MATHEMATICA
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a[n_] := DivisorSum[n, (-1)^(# + n/#)*#^7 &]; Array[a, 25] (* Amiram Eldar, Nov 22 2022 *)
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PROG
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CROSSREFS
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KEYWORD
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sign,mult
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AUTHOR
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STATUS
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approved
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