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Middle European Mathematical Olympiad
2017 Middle European Mathematical Olympiad
7
Partial sums are distinct modulo n
Partial sums are distinct modulo n
Source: MEMO 2017 T7
August 25, 2017
number theory
Problem Statement
Determine all integers
n
≥
2
n \geq 2
n
≥
2
such that there exists a permutation
x
0
,
x
1
,
…
,
x
n
−
1
x_0, x_1, \ldots, x_{n - 1}
x
0
,
x
1
,
…
,
x
n
−
1
of the numbers
0
,
1
,
…
,
n
−
1
0, 1, \ldots, n - 1
0
,
1
,
…
,
n
−
1
with the property that the
n
n
n
numbers
x
0
,
x
0
+
x
1
,
…
,
x
0
+
x
1
+
…
+
x
n
−
1
x_0, \hspace{0.3cm} x_0 + x_1, \hspace{0.3cm} \ldots, \hspace{0.3cm} x_0 + x_1 + \ldots + x_{n - 1}
x
0
,
x
0
+
x
1
,
…
,
x
0
+
x
1
+
…
+
x
n
−
1
are pairwise distinct modulo
n
n
n
.
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