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National and Regional Contests
Russia Contests
239 Open Math Olympiad
2015 239 Open Mathematical Olympiad
2
2
Part of
2015 239 Open Mathematical Olympiad
Problems
(1)
Writing a Binomial Coefficient as Product of $n$ Coprime Numbers
Source: 239 2015 P2
5/14/2020
Prove that
(
n
+
k
n
)
\binom{n+k}{n}
(
n
n
+
k
)
can be written as product of
n
n
n
pairwise coprime numbers
a
1
,
a
2
,
…
,
a
n
a_1,a_2,\dots,a_n
a
1
,
a
2
,
…
,
a
n
such that
k
+
i
k+i
k
+
i
is divisible by
a
i
a_i
a
i
for all indices
i
i
i
.
number theory
binomial coefficients