Did I type it wrong?

$!n$ means subfactorial of n.

$!n= n![\frac{1}{2!} - \frac{1}{3!} +\frac{1}{4!} +--------+\frac{(-1)^{n}}{n!}]$

Now, !4 will be:

And $n!^{k}$ is multi factorial of n of order k. And it's formula can be given as:

And then $9!^{3} or 9!!! =9×6×3=\boxed{162}$ .