Puzzles and logic › Processes, invariants and strategy › Board operations and invariants
Erasing triples on a board
High school · ●●○○○ 20 pts
On a board the numbers are written. One step consists of erasing three numbers from the board and writing in their place the number , where is a fixed positive integer. Determine the positive integer such that, after 13 steps, the number is written on the board.