MathDB
TOT 2006 Spring - Senior A-Level p5 product of infitie numbers

Source:

February 25, 2020
number theorycombinatorics

Problem Statement

Prove that one can find infinite number of distinct pairs of integers such that every digit of each number is no less than 77 and the product of two numbers in each pair is also a number with all its digits being no less than 77. (6)