Periodic Circles (noch nicht übersetzt)

This problem involves an iterative procedure that begins with a circle of $n\ge 3$ integers. At each step every number is simultaneously replaced with the absolute difference of its two neighbours.

For any initial values, the procedure eventually becomes periodic.

Let $S(N)$ be the sum of all possible periods for $3\le n \leq N$. For example, $S(6) = 6$, because the possible periods for $3\le n \leq 6$ are $1, 2, 3$. All these $n$ can have period $1$; in addition $n=5$ can have period $3$ and $n=6$ can have period $2$.

You are also given $S(30) = 20381$.

Find $S(100)$.