The generalized Koebe function
Problemy analiza, no. 17 (2010), pp. 61-66
We observe that the extremal function for $|a_{3}|$ within the class $U'_{\alpha}$ (see Starkov [1]) has as well the property that max $|A_{4}|>4.15$, if $\alpha=2$. The problem is equivalent to the global estimate for Meixner-Pollaczek polynomials $P^{1}_{3}(x;\theta)$.
@article{PA_2010_17_a5,
author = {I. Naraniecka and J. Szynal and A. Tatarczak},
title = {The generalized {Koebe} function},
journal = {Problemy analiza},
pages = {61--66},
year = {2010},
number = {17},
language = {en},
url = {http://geodesic.mathdoc.fr/item/PA_2010_17_a5/}
}
I. Naraniecka; J. Szynal; A. Tatarczak. The generalized Koebe function. Problemy analiza, no. 17 (2010), pp. 61-66. http://geodesic.mathdoc.fr/item/PA_2010_17_a5/
[1] Starkov V. V., “The estimates of coefficients in locally-univalent family $U'_{\alpha}$”, Vestnik Lenin. Gosud. Univ., 13 (1984), 48–54 (In Russian) | MR | Zbl
[2] Koekoek R., Swarttouw R. F., “The Askey-scheme of hypergeometric orthogonal polynomials and its $q$-analogue”, Report 98-17, Delft University of Technology, 1998
[3] Starkov V. V., Linear-invariant families of functions, Dissertation, Ekatirenburg, 1999, 287 pp. (In Russian)