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National and Regional Contests
Mongolia Contests
Mongolian Mathematical Olympiad
2007 Mongolian Mathematical Olympiad
Problem 6
prove number divides sum of a^a
prove number divides sum of a^a
Source: Mongolian MO 2007 Teachers P6
April 8, 2021
number theory
Problem Statement
Let
n
=
p
1
α
1
⋯
p
s
α
s
≥
2
n=p_1^{\alpha_1}\cdots p_s^{\alpha_s}\ge2
n
=
p
1
α
1
⋯
p
s
α
s
≥
2
. If for any
α
∈
N
\alpha\in\mathbb N
α
∈
N
,
p
i
−
1
∤
α
p_i-1\nmid\alpha
p
i
−
1
∤
α
, where
i
=
1
,
2
,
…
,
s
i=1,2,\ldots,s
i
=
1
,
2
,
…
,
s
, prove that
n
∣
∑
α
∈
Z
n
∗
α
α
n\mid\sum_{\alpha\in\mathbb Z^*_n}\alpha^{\alpha}
n
∣
∑
α
∈
Z
n
∗
α
α
where
Z
n
∗
=
{
a
∈
Z
n
:
gcd
(
a
,
n
)
=
1
}
\mathbb Z^*_n=\{a\in\mathbb Z_n:\gcd(a,n)=1\}
Z
n
∗
=
{
a
∈
Z
n
:
g
cd
(
a
,
n
)
=
1
}
.
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