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Turkey MO (2nd round)
1999 Turkey MO (2nd round)
3
Turkey NMO 1999, P-3, the number of the functions
Turkey NMO 1999, P-3, the number of the functions
Source:
December 23, 2010
function
combinatorics proposed
combinatorics
Problem Statement
For any two positive integers
n
n
n
and
p
p
p
, prove that there are exactly
(
p
+
1
)
n
+
1
−
p
n
+
1
{{(p+1)}^{n+1}}-{{p}^{n+1}}
(
p
+
1
)
n
+
1
−
p
n
+
1
functions
f
:
{
1
,
2
,
.
.
.
,
n
}
→
{
−
p
,
−
p
+
1
,
−
p
+
2
,
.
.
.
.
,
p
−
1
,
p
}
f:\left\{ 1,2,...,n \right\}\to \left\{ -p,-p+1,-p+2,....,p-1,p \right\}
f
:
{
1
,
2
,
...
,
n
}
→
{
−
p
,
−
p
+
1
,
−
p
+
2
,
....
,
p
−
1
,
p
}
such that
∣
f
(
i
)
−
f
(
j
)
∣
≤
p
\left| f(i)-f(j) \right|\le p
∣
f
(
i
)
−
f
(
j
)
∣
≤
p
for all
i
,
j
∈
{
1
,
2
,
.
.
.
,
n
}
i,j\in \left\{ 1,2,...,n \right\}
i
,
j
∈
{
1
,
2
,
...
,
n
}
.
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