MathDB
4p^2-8p+1|x_i - (2p)^k odd prime p , x_{n+2}= 4x_{n+1}-x_n

Source: 2006 VMEO III Shortlist SL N3 Vietnamese Mathematics e - Olympiad https://artofproblemsolving.com/community/c2461015_vme

November 24, 2021
number theorydivides

Problem Statement

Given odd prime pp. Sequence xn{x_n} is defined by xn+2=4xn+1xnx_{n+2}= 4x_{n+1}-x_n. Choose x0,x1x_0,x_1 such that for every random positive integer kk, there exists iNi\in \mathbb N such that 4p28p+1xi(2p)k4p^2-8p+1|x_i - (2p)^k.