Friday, 16 August 2013

sequences and series - Strategies for evaluating sums sumin=1nftyfracH(m)nznn

I'm looking for strategies for evaluating the following sums for given z and m:
Sm(z):=n=1H(m)nznn,
where H(m)n is the generalized harmonic number, and |z|<1, mR.



Using the generating function of the generalized harmonic numbers, an equivalent problem is to evaluate the following integral:
Sm(z)=z0Lim(t)t(1t)dt,
where Lim(t) is the polylogarithm function, and |z|<1, mR.




Question 1: Are there any way to reduce the sum to Euler sum values, given by Flajolet–Salvy paper?



Question 2: Are there any way to reduce the integral to integrals given by Freitas paper?








The case m=1 and z=1/2 was the problem 1240 in Mathematics Magazine, Vol. 60, No. 2, pp. 118–119. (Apr., 1987) by Coffman, S. W.
S1(12)=n=1Hnn2n=π212.
There are several solutions in the linked paper.



The more interesting case m=2 and z=1/2 is listed at Harmonic Number, MathWorld, eq. (41):
S2(12)=n=1H(2)nn2n=58ζ(3).



We know less about the evaluation. At the MathWorld it is marked as "B. Cloitre (pers. comm., Oct. 4, 2004)". This value is also listed at pi314.net, eq. (701). Unfortunately, I don't know about any paper/book reference for this value. It would be nice to see some.




Question 3: How could we evaluate the case m=2, z=1/2?




It would be nice to see a solution for the sum form, but also solutions for the integral form are welcome.

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