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Vietnam Team Selection Test
2022 Vietnam TST
5
5
Part of
2022 Vietnam TST
Problems
(1)
Vietnam TST #5
Source: Vietnam TST 2022 P5
4/27/2022
A fractional number
x
x
x
is called pretty if it has finite expression in base
−
b
-b
−
b
numeral system,
b
b
b
is a positive integer in
[
2
;
2022
]
[2;2022]
[
2
;
2022
]
. Prove that there exists finite positive integers
n
≥
4
n\geq 4
n
≥
4
that with every
m
m
m
in
(
2
n
3
;
n
)
(\frac{2n}{3}; n)
(
3
2
n
;
n
)
then there is at least one pretty number between
m
n
−
m
\frac{m}{n-m}
n
−
m
m
and
n
−
m
m
\frac{n-m}{m}
m
n
−
m
base system
combinatorics