MathDB
ARMO 2019, 11.7

Source: All-Russian Math Olimpiad 2019, http://vos.olimpiada.ru/main/table/tasks/#table

July 12, 2019
ARMO

Problem Statement

There are non-constant polynom P(x)P(x) with integral coefficients and natural number nn. Suppose that a0=na_0=n, ak=P(ak1)a_k=P(a_{k-1}) for any natural kk. Finally, for every natural bb there is number in sequence a0,a1,a2,a_0, a_1, a_2, \ldots that is bb-th power of some natural number that is more than 1. Prove that P(x)P(x) is linear polynom.