Wednesday, 14 May 2014

calculus - Interesting Harmonic Sum $sum_{kgeq 1}frac{(-1)^{k-1}}{k^2}H_k^{(2)}$



Here http://integralsandseries.prophpbb.com/topic119.html




We came across the following harmonic sum



$$\tag{1} \sum_{k\geq 1}\frac{(-1)^{k-1}}{k^2}H_k^{(2)}$$



Note that we define



$$H_k^{(2)}=\sum_{n\geq 1}^k\frac{1}{n^2} $$



Also we have




$$\psi_1(k+1)= \zeta(2) -H_k^{(2)} $$



Any ideas how to evaluate (1) ?


Answer



A related problem. You can have the following identity




$$\sum_{k=1}^{\infty}(-1)^{k-1} \frac{H_k^{(2)}}{k^2} = \frac{37}{16}\zeta(4)+2\sum_{k=1}^{\infty}(-1)^k \frac{H_k}{k^3}\sim 0.7843781621 .$$




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