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Problems
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National and Regional Contests
PEN Problems
PEN A Problems
67
67
Part of
PEN A Problems
Problems
(1)
A 67
Source:
5/25/2007
Prove that
(
2
n
n
)
2n \choose n
(
n
2
n
)
is divisible by
n
+
1
n+1
n
+
1
.
Divisibility Theory