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Estimates for the coefficients of univalent functions in terms of the second coefficient
L. P. Il'ina Leningrad State University, USSR
Abstract:
For the coefficients $b_n$ of an odd function $f(z)=z+\sum^\infty_{k=1}b_kz^{2k+1}$, regular in the unit disk, we obtain the estimate
\begin{equation}
|b_n|\le\frac1{\sqrt2}\sqrt{1+|b_1|^2}\exp\frac12(\delta+\frac12|b_1|^2), \quad\text{where}\;\delta=0,312,
\tag{1}
\end{equation}
from which it follows that $|b_n|\le1$, if $|b_1|\le0,524$. It follows from (1) that the coefficients $c_n, n=3, 4\ldots$ of a regular function $f(z)=z+\sum^\infty_{k=2}c_kz^k$, univalent in the unit desk, satisfy
\begin{equation}
|b_n|\le\frac1{\sqrt2}\sqrt{1+|b_1|^2}\exp\frac12(\delta+\frac12|b_1|^2), \quad\text{where}\;\delta=0,312,
\tag{2}
\end{equation}
in particular, $|c_n|\le n$, if $|c_2|\le1,046$.
Received: 04.11.1972
Citation:
L. P. Il'ina, “Estimates for the coefficients of univalent functions in terms of the second coefficient”, Mat. Zametki, 13:3 (1973), 351–357; Math. Notes, 13:3 (1973), 215–218
Linking options:
https://www.mathnet.ru/eng/mzm7130 https://www.mathnet.ru/eng/mzm/v13/i3/p351
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Abstract page: | 184 | Full-text PDF : | 79 | First page: | 1 |
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