Please vote for undeleting this question: https://math.stackexchange.com/questions/4410226. The question really deserves an answer. See the edit history at https://math.stackexchange.com/posts/4410226/revisions. It can be compared to the edit history of a question I asked on another site: https:...

Let's consider the following variant of Collatz $(3n+1) : $ If $n$ is odd then $n \to n^2-1.$ $1\to 0.$ $3\to 8\to 1\to 0.$ $5\to 24\to 3\to 0.$ $7\to 48\to 3\to 0.$ $9\to 80\to 5\to 0.$ $11\to 120\to 15\to 224\to 7\to 0.$ $\color{red}{13\to 168\to 21\to 440\to 55\to 3024\to 189\to 35720\to 4465\...