Lattice Point Connections
Source:
August 8, 2024
combinatorics2022
Problem Statement
Let denote the set of points in 2D space with integer coordinates such that and . That is,
Find the number of ways to connect points of with segments of length or such that the interior of any unit square with vertices in contains part of exactly one segment; an example is shown below (connections that differ by reflections are distinct).
[asy]
unitsize(1cm);
dot((0,0));
dot((1,0));
dot((2,0));
dot((3,0));
dot((4,0));
dot((0,1));
dot((1,1));
dot((2,1));
dot((3,1));
dot((4,1));
dot((0,2));
dot((1,2));
dot((2,2));
dot((3,2));
dot((4,2));
draw((0,0)--(1,1));
draw((0,2)--(2,1));
draw((1,1)--(2,0));
draw((2,0)--(3,2));
draw((3,1)--(4,2));
draw((3,0)--(4,1));
[/asy]