Vietnam TST #6
Source: Vietnam TST 2022 P6
April 27, 2022
set theoryimportant numberscoloringscombinatorics
Problem Statement
Given a set . They color numbers of them by white and the rest of them by black. With each , called the important number of be the number of all white numbers smaller than and black numbers larger than . With every natural number , find all positive integers that exist a way to color the numbers that can get important numbers equal to .