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A321545
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a(n) = Sum_{d|n} (-1)^(d-1)*d^6.
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3
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1, -63, 730, -4159, 15626, -45990, 117650, -266303, 532171, -984438, 1771562, -3036070, 4826810, -7411950, 11406980, -17043519, 24137570, -33526773, 47045882, -64988534, 85884500, -111608406, 148035890, -194401190, 244156251, -304089030, 387952660, -489306350, 594823322, -718639740, 887503682
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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^6*x^k/(1 - x^k). - Ilya Gutkovskiy, Dec 23 2018
Multiplicative with a(2^e) = 2 - (2^(6*e + 6) - 1)/63, and a(p^e) = (p^(6*e + 6) - 1)/(p^6 - 1) for p > 2. - Amiram Eldar, Nov 04 2022
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MATHEMATICA
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f[p_, e_] := (p^(6*e + 6) - 1)/(p^6 - 1); f[2, e_] := 2 - (2^(6*e + 6) - 1)/63; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 30] (* Amiram Eldar, Nov 04 2022 *)
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PROG
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(PARI) apply( a(n)=sumdiv(n, d, (-1)^(d-1)*d^6), [1..30]) \\ M. F. Hasler, Nov 26 2018
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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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