MathDB
colouring the floor's window of three 2025 floor buidings with 3 colors

Source: Indonesia MO (INAMO) 2015 P8

September 14, 2018
combinatoricsColoring

Problem Statement

It is known that there are 33 buildings in the same shape which are located in an equilateral triangle. Each building has a 20152015 floor with each floor having one window. In all three buildings, every 11st floor is uninhabited, while each floor of others have exactly one occupant. All windows will be colored with one of red, green or blue. The residents of each floor of a building can see the color of the window in the other buildings of the the same floor and one floor just below it, but they cannot see the colors of the other windows of the two buildings. Besides that, sresidents cannot see the color of the window from any floor in the building itself. For example, resident of the 1010th floor can see the colors of the 99th and 1010th floor windows for the other buildings (a total of 44 windows) and he can't see the color of the other window. We want to color the windows so that each resident can see at lest 11 window of each color. How many ways are there to color those windows?