Example 5 For which , can the vertices of a regular -gon be colored using no more than 6 colors, such that any 5 consecutive vertices have distinct colors?
Solution
Let the colors be . Define the sequence and the sequence .
If there exist non-negative integers , such that , then for a regular -gon, the vertices can be colored by first coloring sequences of , followed by sequences of , ensuring that any 5 consecutive vertices are of different colors.
Using the conclusion from Example 3, we know that when , the equation always has non-negative integer solutions. For , direct calculation shows that the equation has no non-negative integer solutions only when .
On the other hand, for , there exists such that . Therefore, there must be a color that appears times. Since these points of the same color are at least 4 points apart, we have
Now,
when , , requiring , which is a contradiction.
when , , requiring , which is a contradiction.
when , , requiring , which is also a contradiction.
In summary, when , except for the numbers in the set , all other positive integers meet the requirement.