Alpan, G.2018-04-122018-04-1220161617-9447http://hdl.handle.net/11693/36883Let (fn)n=1∞ be a sequence of non-linear polynomials satisfying some mild conditions. Furthermore, let Fm(z) : = (fm∘ fm - 1⋯ ∘ f1) (z) and ρm be the leading coefficient of Fm. It is shown that on the Julia set J(fn), the Chebyshev polynomial of degree deg Fm is of the form Fm(z) / ρm- τm for all m∈ N where τm∈ C. This generalizes the result obtained for autonomous Julia sets in Kamo and Borodin (Mosc. Univ. Math. Bull. 49:44–45, 1994). © 2015, Springer-Verlag Berlin Heidelberg.EnglishChebyshev polynomialsExtremal polynomialsJulia setsWidom factorsArticle10.1007/s40315-015-0145-82195-3724