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Problems
Contests
National and Regional Contests
India Contests
Postal Coaching
2008 Postal Coaching
1
LCM identity with combinations
LCM identity with combinations
Source: Indian Postal Coaching 2008 set 3 p1
May 25, 2020
number theory
least common multiple
LCM
Combinations
Problem Statement
Prove that for any
n
≥
1
n \ge 1
n
≥
1
,
L
C
M
0
≤
k
≤
n
{
LCM _{0\le k\le n} \big \{
L
C
M
0
≤
k
≤
n
{
(
n
k
)
n \choose k
(
k
n
)
}
=
1
n
+
1
L
C
M
{
1
,
2
,
3
,
.
.
.
,
n
+
1
}
\big\} = \frac{1}{n + 1} LCM \{1, 2,3,...,n + 1\}
}
=
n
+
1
1
L
CM
{
1
,
2
,
3
,
...
,
n
+
1
}
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