Can someone help me to evaluate the following sum. It appeared while calculating the number of elements of intersections of some sets: $$\sum_{d|n} \frac{d}{\phi(d)^2}.$$
Can someone help me to evaluate or at least to approximate the following sum.
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number-theory
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1It looks to be a multiplicative function, and the result for prime powers is somewhat tractable. Have you already looked at it to that extent? – 2012-07-07
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0To extend on hardmath's finding I got indeed $f(p)=\frac{p^2-p+1}{(p-1)^2}$ (the 'distribution' obtained is very regular with a mean value of $\approx 3.39063$) – 2012-07-07