Fekete–Szegö problem for starlike and convex functions of complex order

For nonzero complex b let F n ( b ) denote the class of normalized univalent functions f satisfying Re  [ 1 + ( z ( D n f ) ′ ( z ) / D n f ( z ) − 1 ) / b ] > 0 in the unit disk U , where D n f denotes the Ruscheweyh derivative of f . Sharp bounds for the Fekete–Szegö functional | a 3 − μ a 2 2 | are obtained.