MathDB

2

Part of 2021 Benelux

Problems(1)

Distinct pebble sets (BxMO2021 P2)

Source: BxMO2021 problem 2

5/3/2021
Pebbles are placed on the squares of a 2021×20212021\times 2021 board in such a way that each square contains at most one pebble. The pebble set of a square of the board is the collection of all pebbles which are in the same row or column as this square. (A pebble belongs to the pebble set of the square in which it is placed.) What is the least possible number of pebbles on the board if no two squares have the same pebble set?
BxMOcombinatorics