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5
2018 November Team #5
2018 November Team #5
Source:
November 13, 2018
Problem Statement
Find the sum of all positive integers
n
n
n
such that
1
+
2
+
⋯
+
n
1+2+\cdots+n
1
+
2
+
⋯
+
n
divides
15
[
(
n
+
1
)
2
+
(
n
+
2
)
2
+
⋯
+
(
2
n
)
2
]
.
15\left[(n+1)^2+(n+2)^2+\cdots+(2n)^2\right].
15
[
(
n
+
1
)
2
+
(
n
+
2
)
2
+
⋯
+
(
2
n
)
2
]
.
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