BG-MO 2022 Problem 1
A white equilateral triangle with side length is divided into equilateral triangles with side (cells) by lines parallel to the sides of . We'll call two cells if they have a common vertex. Ivan colours some of the cells in black. Without knowing which cells are black, Peter chooses a set of cells and Ivan tells him the parity of the number of black cells in . After knowing this, Peter is able to determine the parity of the number of cells of different colours. Find all possible cardinalities of such that this is always possible independent of how Ivan chooses to colour the cells.
Dataset text AI-MO AoPS. 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.
Similar problems
These problems have the most words in common with this statement.