BeeHive!!!
Source: 11th XMO #4
February 13, 2023
combinatorics
Problem Statement
We define a beehive of order as follows:a beehive of order 1 is one hexagonTo construct a beehive of order , take a beehive of order and draw a layer of hexagons in the exterior of these hexagons. See diagram for examples of Initially some hexagons are infected by a virus. If a hexagon has been infected, it will always be infected. Otherwise, it will be infected if at least 5 out of the 6 neighbours are infected.Let be the minimum number of infected hexagons in the beginning so that after a finite time, all hexagons become infected. Find .