natural a is said to be contained in natural number b, (combo related)
Source: 2022 Baltic Way p10
November 13, 2022
combinatoricsnumber theory
Problem Statement
A natural number is said to be contained in the natural number if it is possible to obtain a by erasing some digits from (in their decimal representations). For example, is contained in , but not contained in .
Does there exist an infinite set of natural numbers such that no number in the set is contained in any other number from the set?