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2021-IMOC
N10
IMOC 2021 N10
IMOC 2021 N10
Source: IMOC 2021 N10
August 11, 2021
number theory
IMOC
Problem Statement
A prime is called perfect if there is a permutation
a
1
,
a
2
,
⋯
,
a
p
−
1
2
,
b
1
,
b
2
,
⋯
,
b
p
−
1
2
a_1, a_2, \cdots, a_{\frac{p-1}{2}}, b_1, b_2, \cdots, b_{\frac{p-1}{2}}
a
1
,
a
2
,
⋯
,
a
2
p
−
1
,
b
1
,
b
2
,
⋯
,
b
2
p
−
1
of
1
,
2
,
⋯
,
p
−
1
1, 2, \cdots, p-1
1
,
2
,
⋯
,
p
−
1
satisfies
b
i
≡
a
i
+
1
a
i
(
m
o
d
p
)
b_i \equiv a_i + \frac{1}{a_i} \pmod p
b
i
≡
a
i
+
a
i
1
(
mod
p
)
for all
1
≤
i
≤
p
−
1
2
1 \le i \le \frac{p-1}{2}
1
≤
i
≤
2
p
−
1
. Show that there are infinitely many primes that are not perfect.Proposed By - CSJL
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