1
n

n ∙ n ‒ 1
n ∙ (n ‒ 1) ∙ (n ‒ 2)


1 + n + n ∙ (n ‒ 1) + n ∙ (n ‒ 1) ∙ (n ‒ 2)
n!
n!
+
n!
(n ‒ 1)!
+
n!
(n ‒ 2)!
+
n!
(n ‒ 3)!

n! (
1
n!
+ (
1
(n ‒ 1)!
+
1
(n ‒ 2)!
+ ‒
1
3!
+
1
2!
+ 1)