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A357819
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Denominators of the partial sums of the reciprocals of the Dedekind psi function (A001615).
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1
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1, 3, 12, 4, 12, 1, 8, 24, 24, 72, 72, 36, 252, 504, 126, 504, 504, 504, 2520, 840, 3360, 10080, 10080, 10080, 2016, 2016, 2016, 2016, 10080, 10080, 5040, 1260, 5040, 15120, 7560, 3780, 71820, 17955, 143640, 17955, 35910, 574560, 6320160, 6320160, 6320160, 6320160
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OFFSET
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1,2
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COMMENTS
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LINKS
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FORMULA
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a(n) = denominator(Sum_{k=1..n} 1/psi(k)).
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MATHEMATICA
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psi[n_] := n * Times @@ (1 + 1/Transpose[FactorInteger[n]][[1]]); psi[1] = 1; Denominator[Accumulate[1/Array[psi[#] &, 50]]]
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PROG
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(PARI) f(n) = n * sumdivmult(n, d, issquarefree(d)/d); \\ A001615
a(n) = denominator(sum(k=1, n, 1/f(k))); \\ Michel Marcus, Oct 15 2022
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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