Explicit Evaluation of Some Quadratic Euler-Type Sums Containing Double-Index Harmonic Numbers

In this paper a number of new explicit expressions for quadratic Euler-type sums containing double-index harmonic numbers H_2n are given. These are obtained using ordinary generating functions containing the square of the harmonic numbers H_n. As a by-product of the generating function approach used new proofs for the remarkable quadratic series of Au-Yeung ∑n=1∞(Hnn)2=17π4360\sum\limits_{n = 1}^\infty {{{\left( {{{{H_n}} \over n}} \right)}^2} = {{17{\pi ^4}} \over {360}}} together with its closely related alternating cousin are given. New proofs for other closely related quadratic Euler-type sums that are known in the literature are also obtained.