Question 984076
<pre>
The formula for the number of "derangements", or the ways a given 
n-permutation can be rearranged so that every element moves to a new 
position is called n-subfactorial, and is denoted by !n, the 
exclamation mark is before the number instead of after it like 
a regular factorial.

The formula is

{{{"!n"}}}{{{""=""}}}{{{matrix(1,6,the, greatest,integer,not,exceeding,n!/e)}}},
where  e = 2.718281828459045235360287471352662497757247093699959574966967...

Edwin</pre>