I know this is an extremely noob question, but I need some help. since I am stuck
Prove the formula
$$p(n,r) = \frac{(n + 1 -r) \; (r^2 - 3r + 3) \; (r-2)!}{n!}$$
from this answer.
I know this is an extremely noob question, but I need some help. since I am stuck
Prove the formula
$$p(n,r) = \frac{(n + 1 -r) \; (r^2 - 3r + 3) \; (r-2)!}{n!}$$
from this answer.