Asymptotic approximation by de la Vallée Poussin means and their derivatives Original Research Article

The concern of this paper is the study of local approximation properties of the de la Vallée Poussin means Vn. We derive the complete asymptotic expansion of the operators Vn and their derivatives as n tends to infinity. It turns out that the appropriate representation is a series of reciprocal factorials. All coefficients are calculated explicitly.