Puzzles:
1-10
11-20
21-30
31-40
41-50
51-60
61-70
71-80
81-90
91-100
101-110
111-120
121-130
131-140
141-150
151-160
Index
|
Home
About
Accessibility
Answer to puzzle 69: Combinatorial sum
= n
2
(n
3
+ 10n
2
+ 15n − 10) · 2
n−5
