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Sequences and Number theory

Source: Federal Mathematical Competition of Serbia and Montenegro 2004

May 14, 2018
number theory

Problem Statement

The sequence (an)(a_n) is determined by a1=0a_1 = 0 and (n+1)3an+1=2n2(2n+1)an+2(3n+1)(n+1)^3a_{n+1} = 2n^2(2n+1)a_n+2(3n+1) for n1n \geq 1. Prove that infinitely many terms of the sequence are positive integers.