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Weird knight move

Source: Lusophon Mathematical Olympiad 2021 Problem 2

December 19, 2021
Easy Combinatorics

Problem Statement

Esmeralda has created a special knight to play on quadrilateral boards that are identical to chessboards. If a knight is in a square then it can move to another square by moving 1 square in one direction and 3 squares in a perpendicular direction (which is a diagonal of a 2×42\times4 rectangle instead of 2×32\times3 like in chess). In this movement, it doesn't land on the squares between the beginning square and the final square it lands on.
A trip of the length nn of the knight is a sequence of nn squares C1,C2,...,CnC1, C2, ..., Cn which are all distinct such that the knight starts at the C1C1 square and for each ii from 11 to n1n-1 it can use the movement described before to go from the CiCi square to the C(i+1)C(i+1).
Determine the greatest NNN \in \mathbb{N} such that there exists a path of the knight with length NN on a 5×55\times5 board.