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Sequence of polynomials divisible by p

Source: Germany 2011 - Problem 6

December 6, 2022
algebrapolynomialnumber theorySequenceprime

Problem Statement

Let p>2p>2 be a prime. Define a sequence (Qn(x))(Q_{n}(x)) of polynomials such that Q0(x)=1,Q1(x)=xQ_{0}(x)=1, Q_{1}(x)=x and Qn+1(x)=xQn(x)+nQn1(x)Q_{n+1}(x) =xQ_{n}(x) + nQ_{n-1}(x) for n1.n\geq 1. Prove that Qp(x)xpQ_{p}(x)-x^p is divisible by pp for all integers x.x.