reciprocals of every non-zero digit of integers from 1 to 10^n is integer
Source: 2019 Dürer Math Competition Finals Day2 E+7 https://artofproblemsolving.com/community/c1621835_2019_
January 5, 2022
number theoryInteger
Problem Statement
Find the smallest positive integer with the following property: if we write down all positive integers from to and add together the reciprocals of every non-zero digit written down, we obtain an integer.