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Vietnam National Olympiad
2011 Vietnam National Olympiad
2
Show that the sequence has finite limits - [VMO 2011]
Show that the sequence has finite limits - [VMO 2011]
Source:
January 11, 2011
limit
algebra proposed
algebra
Problem Statement
Let
⟨
x
n
⟩
\langle x_n\rangle
⟨
x
n
⟩
be a sequence of real numbers defined as
x
1
=
1
;
x
n
=
2
n
(
n
−
1
)
2
∑
i
=
1
n
−
1
x
i
x_1=1; x_n=\dfrac{2n}{(n-1)^2}\sum_{i=1}^{n-1}x_i
x
1
=
1
;
x
n
=
(
n
−
1
)
2
2
n
i
=
1
∑
n
−
1
x
i
Show that the sequence
y
n
=
x
n
+
1
−
x
n
y_n=x_{n+1}-x_n
y
n
=
x
n
+
1
−
x
n
has finite limits as
n
→
∞
.
n\to \infty.
n
→
∞.
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