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China Team Selection Test
1989 China Team Selection Test
1
Does there exist a function f^{1989}(n) = 2n
Does there exist a function f^{1989}(n) = 2n
Source: China TST 1989, problem 5
June 27, 2005
function
algebra unsolved
algebra
Problem Statement
Let
N
=
{
1
,
2
,
…
}
.
\mathbb{N} = \{1,2, \ldots\}.
N
=
{
1
,
2
,
…
}
.
Does there exists a function
f
:
N
↦
N
f: \mathbb{N} \mapsto \mathbb{N}
f
:
N
↦
N
such that
∀
n
∈
N
,
\forall n \in \mathbb{N},
∀
n
∈
N
,
f
1989
(
n
)
=
2
⋅
n
f^{1989}(n) = 2 \cdot n
f
1989
(
n
)
=
2
⋅
n
?
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