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if f([{\sqrt n}]+ b)divides f(n+a) .. then f{{a}_{i} divides f({{a}_{i+1}})

Source: SRMC 2016

September 2, 2018
floor functioncoprimeDivisibilitynumber theory

Problem Statement

Given natural numbers a,ba,b and function f:NNf: \mathbb{N} \to \mathbb{N} such that for any natural number n,f(n+a)n, f\left( n+a \right) is divided by f([n]+b)f\left( {\left[ {\sqrt n } \right] + b} \right). Prove that for any natural nn exist nn pairwise distinct and pairwise relatively prime natural numbers a1{{a}_{1}}, a2{{a}_{2}}, \ldots, an{{a}_{n}} such that the number f(ai+1)f\left( {{a}_{i+1}} \right) is divided by f(ai)f\left( {{a}_{i}} \right) for each i=1,2,,n1i=1,2, \dots ,n-1 .
(Here [x][x] is the integer part of number xx, that is, the largest integer not exceeding xx.)