Perhaps check it again,
It was my suspicion that you did not expect the factorial character to be used in the manner of a subfactorial. I also guessed you were not aware of the multifactorial notation a!(b), sometimes written a!(b), a!b, or a!b such that a ∉ ℤ- where a mod b = 0, and b ∈ ℤ+, but more often recognized with b (i.e., multiple) factorial characters following the number. Of course it would be difficult to find a solution for the multifactorial given the limitation of three 8's and the other notation symbols.
There indeed is a special character (i.e., a single code point) for the double factorial character -- just as I had used in my post for the double factorial -- hence my question about concatenation with the symbol. Of course, two factorial characters are often used in ASCII notation, as the code point is extended out of the normal ASCII range.