MathDB
Problems
Contests
Undergraduate contests
SEEMOUS
2024 SEEMOUS
P1
P1
Part of
2024 SEEMOUS
Problems
(1)
Recursive sequence has convergent power series
Source: SEEMOUS 2024, Problem 1
4/16/2024
Let
(
x
n
)
n
≥
1
(x_n)_{n\geq 1}
(
x
n
)
n
≥
1
be the sequence defined by
x
1
∈
(
0
,
1
)
x_1\in (0,1)
x
1
∈
(
0
,
1
)
and
x
n
+
1
=
x
n
−
x
n
2
n
x_{n+1}=x_n-\frac{x_n^2}{\sqrt{n}}
x
n
+
1
=
x
n
−
n
x
n
2
for all
n
≥
1
n\geq 1
n
≥
1
. Find the values of
α
∈
R
\alpha\in\mathbb{R}
α
∈
R
for which the series
∑
n
=
1
∞
x
n
α
\sum_{n=1}^{\infty}x_n^{\alpha}
∑
n
=
1
∞
x
n
α
is convergent.
real analysis
college contests