MathDB
Infinite sequence contains an even number

Source: Tournament of Towns, Fall 2002, Senior O Level, P5

May 17, 2014
floor functionnumber theory proposednumber theory

Problem Statement

An infinite sequence of natural number {xn}n1\{x_n\}_{n\ge 1} is such that xn+1x_{n+1} is obtained by adding one of the non-zero digits of xnx_n to itself. Show this sequence contains an even number.