Problem

Source: 2016 Peru MO (ONEM) L3 p2 - finals

Tags: combinatorics, dominoes, tiles, Tiling



How many dominoes can be placed on a at least $3 \times 12$ board, such so that it is impossible to place a $1\times 3$, $3 \times 1$, or $ 2 \times 2$ tile on what remains of the board? Clarification: Each domino covers exactly two squares on the board. The chips cannot overlap.