MathDB
Problems
Contests
National and Regional Contests
Korea Contests
Korea National Olympiad
2022 Korea National Olympiad
4
Cute counting
Cute counting
Source: KMO 2022 P4
October 29, 2022
inequalities
combinatorics
Problem Statement
For positive integers
m
,
n
m, n
m
,
n
(
m
>
n
m>n
m
>
n
),
a
n
+
1
,
a
n
+
2
,
.
.
.
,
a
m
a_{n+1}, a_{n+2}, ..., a_m
a
n
+
1
,
a
n
+
2
,
...
,
a
m
are non-negative integers that satisfy the following inequality.
2
>
a
n
+
1
n
+
1
≥
a
n
+
2
n
+
2
≥
⋯
≥
a
m
m
2> \frac{a_{n+1}}{n+1} \ge \frac{a_{n+2}}{n+2} \ge \cdots \ge \frac{a_m}{m}
2
>
n
+
1
a
n
+
1
≥
n
+
2
a
n
+
2
≥
⋯
≥
m
a
m
Find the number of pair
(
a
n
+
1
,
a
n
+
2
,
⋯
,
a
m
)
(a_{n+1}, a_{n+2}, \cdots, a_m)
(
a
n
+
1
,
a
n
+
2
,
⋯
,
a
m
)
.
Back to Problems
View on AoPS