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Perfect polynomials

Source: 2023 Israel TST Test 5 P3

March 23, 2023
TSTnumber theoryPolynomialscompositionalgebra

Problem Statement

Given a polynomial PP and a positive integer kk, we denote the kk-fold composition of PP by PkP^{\circ k}. A polynomial PP with real coefficients is called perfect if for each integer nn there is a positive integer kk so that Pk(n)P^{\circ k}(n) is an integer. Is it true that for each perfect polynomial PP, there exists a positive mm so that for each integer nn there is 0<km0<k\leq m for which Pk(n)P^{\circ k}(n) is an integer?