k-knight visits cells on a grid
Source: APMO 2024 P2
July 29, 2024
combinatoricsAPMO 2024
Problem Statement
Consider a table, and identify the cell in row and column , , with the ordered pair . Let be an integer such that . A -knight is a piece that moves one cell vertically or horizontally and cells to the other direction; that is, it moves from to such that is either or . The -knight starts at cell , and performs several moves. A sequence of moves is a sequence of cells , , such that, for all , and the -knight can move from to . In this case, each cell is said to be reachable. For each , find , the number of reachable cells.