MathDB
Rootiful sets

Source: IMO 2019 SL N3

September 22, 2020
number theoryIMO ShortlistIMO Shortlist 2019polynomial

Problem Statement

We say that a set SS of integers is rootiful if, for any positive integer nn and any a0,a1,,anSa_0, a_1, \cdots, a_n \in S, all integer roots of the polynomial a0+a1x++anxna_0+a_1x+\cdots+a_nx^n are also in SS. Find all rootiful sets of integers that contain all numbers of the form 2a2b2^a - 2^b for positive integers aa and bb.