MathDB
compatible numbers

Source: Mexico 2003

March 2, 2007
combinatorics unsolvedcombinatorics

Problem Statement

Given a positive integer nn, an allowed move is to form 2n+12n+1 or 3n+23n+2. The set SnS_{n} is the set of all numbers that can be obtained by a sequence of allowed moves starting with nn. For example, we can form 511355 \rightarrow 11 \rightarrow 35 so 5,115, 11 and 3535 belong to S5S_{5}. We call mm and nn compatible if SmS_{m} and SnS_{n} has a common element. Which members of {1,2,3,...,2002}\{1, 2, 3, ... , 2002\} are compatible with 20032003?