Our paper [2] was published in Vol. 425 of Zapiski POMI (English transl. in J. Math. Sci., 210, No. 6, 779–786 (2015)). Prof. I. A. Sheipak kindly pointed us out that the final formulas in [2, Theorem 2] are wrong. Correct values of the sharp constants are as follows: (Formula presented.) (Formula presented.) Note that the values of the sharp constants λ(r, k, 2,∞) for all even k < r and the proof of symmetry for corresponding extremal functions is given by T. A. Garmanova and I. A. Sheipak in [1].