MathDB
larger number is a multiple of the smaller number

Source: China TST 1996, problem 3

May 17, 2005
combinatorics unsolvedcombinatorics

Problem Statement

Let M \equal{} \lbrace 2, 3, 4, \ldots\, 1000 \rbrace. Find the smallest nN n \in \mathbb{N} such that any n n-element subset of M M contains 3 pairwise disjoint 4-element subsets S,T,U S, T, U such that I. For any 2 elements in S S, the larger number is a multiple of the smaller number. The same applies for T T and U U. II. For any sS s \in S and tT t \in T, (s,t) \equal{} 1. III. For any sS s \in S and uU u \in U, (s,u)>1 (s,u) > 1.