“…For α, β, μ real numbers, let P α,β, μ (r, s) = r α μ−β s β−1 (r α + s α ) −μ for all r, s > 0. The spectral properties of its associated Hardy operator have been studied in [16]. Regarding the properties considered in the present paper, we have that, for p ∈ [1, ∞) and α > 0, P α,β, μ ∈ H p if and only if 0 < β − 1/p < αμ, and in this case, P α,β, μ ∈ I p .…”