infinite sequence of numbered lights (2023 Auckland MO p6)
Source:
March 26, 2024
combinatoricsnumber theory
Problem Statement
Suppose there is an infinite sequence of lights numbered and you know the following two rules about how the lights work:
If the light numbered is on, the lights numbered and are also guaranteed to be on.
If the light numbered is off, then the lights numbered and are also guaranteed to be off.
Suppose you notice that light number is on. Identify all the lights that are guaranteed to be on?