MathDB
APMO 2015 P3

Source: APMO 2015

March 30, 2015
number theoryAPMOSequence

Problem Statement

A sequence of real numbers a0,a1,...a_0, a_1, . . . is said to be good if the following three conditions hold. (i) The value of a0a_0 is a positive integer. (ii) For each non-negative integer ii we have ai+1=2ai+1a_{i+1} = 2a_i + 1 or ai+1=aiai+2a_{i+1} =\frac{a_i}{a_i + 2} (iii) There exists a positive integer kk such that ak=2014a_k = 2014.
Find the smallest positive integer nn such that there exists a good sequence a0,a1,...a_0, a_1, . . . of real numbers with the property that an=2014a_n = 2014.
Proposed by Wang Wei Hua, Hong Kong