RU-ALLRUSSIAN 1973 Problem 8
At time 1, n unit squares of an infinite sheet of paper ruled in squares are painted black, the rest remain white. At time , the color of each square is changed to the color held at time k by a majority of the following three squares: the square itself, its northern neighbour and its eastern neighbour. Prove that all the squares are white at time .
Dataset text NuminaMath olympiads. Quoted with source.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.