Randomize a List problem

[Hlib]

Thanks everyone!
In our examples, can we estimate the number of different combinations for lists of any size? There may be unexpected results.
I inserted a fragment into the source program, which swaps 1-st and random n-th elements on stack:

Code:

<< { } LIST➝ ➝ t
<< 1. t FOR n t RAND × CEIL
PICK LASTARG SWAP UNROT UNPICK
NEXT t ➝LIST >> >>

Results are:
#2 {2 1} – 2 options out of 2!=2 possible.
#3 {3 2 1} – 6 options out of 3!=6 possible.
#4 {4 3 2 1} – 24 / out of 4!=24.
#5 {5 4 3 2 1} – 107=5!–13 / out of 5!=120.
#6 {6 5 4 3 2 1} – 685=6!–35 / out of 6!=720.
For many practical problems we don`t need to have equal probabilities for each permutation, and we don`t always need the maximum number of possible combinations. But in these short programs before using them I would like to estimate at least the range of results that we get using the stack process.