Abstract
LesB denote the class of functions analytic in the unit disc ofC which satisfy 0<|f(z)|<1. It is proved that there exists a numberc<1 such that iff∈B and iff(z)=Σ ∞ n=0 a n z n, then |a n |<c forn>=1.
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Horowitz, C. Coefficients of nonvanishing functions inH ∞ . Israel J. Math. 30, 285–291 (1978). https://doi.org/10.1007/BF02761076
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DOI: https://doi.org/10.1007/BF02761076