subfactorial...the total permutations of n elements excluding those that contain elements in their natural place
ie: !3 = 2
123, 132, 213, 321, all contain at least one element where it should be leaving only 132, and 312
!1 = 0, !2 = 1, !3 = 2, !4 = 9...
(though you got me on the 3 fours though! 😵 )
Originally posted by AgergNice. I found an article in wikipedia about this. This can really be helpful. Only you need four, not three 4's in the expression.
subfactorial...the total permutations of n elements excluding those that contain elements in their natural place
ie: !3 = 2
123, 132, 213, 321, all contain at least one element where it should be leaving only 132, and 312
(though you got me on the 3 fours though! 😵 )
Oops, didn't see your edit.