MathDB
2002 KJMO P4

Source: KJMO 2002

June 29, 2024
number theory

Problem Statement

For two non-negative integers i,ji, j, create a new integer i#ji \# j defined as the following: Express the two numbers in base 22, and compare each digit. If their kkth digit is the same, then the kkth digit of i#ji \# j is 00. If their kkth digit is different, then the kkth digit of i#ji \# j is 11(of course we are talking in base 22). For instance, 3#5=63 \# 5=6. Show that for arbitrary positive integer nn, the number can be expressed with finite operations of #\#s and integers of the form 2kāˆ’12^k-1.