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India STEMS
2024 India STEMS
STEMS 2024 Math Cat A
P5
P5
Part of
STEMS 2024 Math Cat A
Problems
(1)
find the maximum value of t so that b_n becomes unbounded
Source: STEMS 2024, CAT B - P3, CAT A - P5
12/17/2023
Let
r
r
r
,
s
s
s
be real numbers, find maximum
t
t
t
so that if
a
1
,
a
2
,
…
a_1, a_2, \ldots
a
1
,
a
2
,
…
is a sequence of positive real numbers satisfying
a
1
r
+
a
2
r
+
⋯
+
a
n
r
≤
2023
⋅
n
t
a_1^r + a_2^r + \cdots + a_n^r \le 2023 \cdot n^t
a
1
r
+
a
2
r
+
⋯
+
a
n
r
≤
2023
⋅
n
t
for all
n
≥
2023
n \ge 2023
n
≥
2023
then the sum
b
n
=
1
a
1
s
+
⋯
+
1
a
n
s
b_n = \frac 1{a_1^s} + \cdots + \frac 1{a_n^s}
b
n
=
a
1
s
1
+
⋯
+
a
n
s
1
is unbounded, i.e for all positive reals
M
M
M
there is an
n
n
n
such that
b
n
>
M
b_n > M
b
n
>
M
.
algebra