Hankel determinant H2,3 for starlike and convex functions

Abstract

Let f be analytic in the unit disk D={z∈C:|z|<1}. We obtain bounds of |H2,3|, where H2,3=a3a5−a42 for two classes S⁎ and K consisting of starlike and convex univalent functions, respectively. Additionally, we derive the sharp upper bounds of H2,3 in case of real coefficients.