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Problems
Contests
National and Regional Contests
Switzerland Contests
Switzerland Team Selection Test
2016 Switzerland Team Selection Test
Problem 7
Problem 7
Part of
2016 Switzerland Team Selection Test
Problems
(1)
sum of square of divisors
Source: Swiss IMO TST 2016. Problem 7
7/27/2017
Find all positive integers
n
n
n
such that
∑
d
∣
n
,
1
≤
d
<
n
d
2
=
5
(
n
+
1
)
\sum_{d|n, 1\leq d <n}d^2=5(n+1)
d
∣
n
,
1
≤
d
<
n
∑
d
2
=
5
(
n
+
1
)
number theory
Divisors