On an infinite series of Abel occurring in the theory of interpolation

Abstract

AbstractThe purpose of this paper is to show that for a certain class of functions f which are analytic in the complex plane possibly minus (−∞, −1], the Abel series f(0) + Σn = 1∞ f(n)(nβ) z(z − nβ)n − 1n! is convergent for all β>0. Its sum is an entire function of exponential type and can be evaluated in terms of f. Furthermore, it is shown that the Abel series of f for small β>0 approximates f uniformly in half-planes of the form Re(z) ⩾ − 1 + δ, δ>0. At the end of the paper some special cases are discussed