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2023 Korea National Olympiad
5
phi sigma
phi sigma
Source: KMO 2023 P5
November 4, 2023
number theory
Problem Statement
Find all positive integers
n
n
n
such that
ϕ
(
n
)
+
σ
(
n
)
=
2
n
+
8.
\phi(n) + \sigma(n) = 2n + 8.
ϕ
(
n
)
+
σ
(
n
)
=
2
n
+
8.
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