As in, "The Hitchhiker's Guide". Sandra says, "Rule of thumb: number of shafts, squared, less 2 = number of possible combinations of shafts that can be lifted." You don't want to know how many times I tried to figure this out.
EDIT: I made a flippant remark here and in the comment and now I have to dig up some old notebooks in the margins of which I may have made comments/observations, since I used to think about this a lot. Although there is also the possibility I got rid of those notebooks; we'll see.
Meanwhile, I tended to see shaft lifting combinations as combination with no repetitions. Today, Thursday, while rechecking the formula, (one of very few I remember from junior high,) I found a website that included information on Pascal's Triangle Cally mentioned. So I add the link for your reading pleasure.
I'm relieved Sandra has given us the formula, but I would like to try and recall if I was so off track or pretty much on course. Not that that's gonna make much difference to how or what I want to weave.