MathDB
Problems
Contests
International Contests
Lusophon Mathematical Olympiad
2021 Lusophon Mathematical Olympiad
2
2
Part of
2021 Lusophon Mathematical Olympiad
Problems
(1)
Weird knight move
Source: Lusophon Mathematical Olympiad 2021 Problem 2
12/19/2021
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
×
4
2\times4
2
×
4
rectangle instead of
2
×
3
2\times3
2
×
3
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
n
n
n
of the knight is a sequence of
n
n
n
squares
C
1
,
C
2
,
.
.
.
,
C
n
C1, C2, ..., Cn
C
1
,
C
2
,
...
,
C
n
which are all distinct such that the knight starts at the
C
1
C1
C
1
square and for each
i
i
i
from
1
1
1
to
n
−
1
n-1
n
−
1
it can use the movement described before to go from the
C
i
Ci
C
i
square to the
C
(
i
+
1
)
C(i+1)
C
(
i
+
1
)
.Determine the greatest
N
∈
N
N \in \mathbb{N}
N
∈
N
such that there exists a path of the knight with length
N
N
N
on a
5
×
5
5\times5
5
×
5
board.
Easy Combinatorics