max gcd of all 2022-digit numbers using only 1 and 7
Source: 2022 South Russian Girls MO - Assara Juniors p4
February 28, 2024
number theorygreatest common divisor
Problem Statement
Nadya has cards, each with a number one or seven written on it. It is known that there are both cards.Nadya looked at all possible -digit numbers that can be composed from all these cards. What is the largest value that can take the greatest common divisor of all these numbers?