I have the following term : $\log_2 (3\cdot6\cdot9\cdot...\cdot(n -1 - ((n - 1)$ mod $3))$.
Unfortunately, i don't know how to reduce this form. I think that the input term is equal to $\log (\frac{n}{3}!)$, but i'm not convinced in it. So what is the concise representation of the input term?