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Putnam
1954 Putnam
A6
Putnam 1954 A6
Putnam 1954 A6
Source: Putnam 1954
July 17, 2022
Putnam
Sequence
real numbers
Problem Statement
Suppose that
u
0
,
u
1
,
…
u_0 , u_1 ,\ldots
u
0
,
u
1
,
…
is a sequence of real numbers such that
u
n
=
∑
k
=
1
∞
u
n
+
k
2
for
n
=
0
,
1
,
2
,
…
u_n = \sum_{k=1}^{\infty} u_{n+k}^{2}\;\;\; \text{for} \; n=0,1,2,\ldots
u
n
=
k
=
1
∑
∞
u
n
+
k
2
for
n
=
0
,
1
,
2
,
…
Prove that if
∑
u
n
\sum u_n
∑
u
n
converges, then
u
k
=
0
u_k=0
u
k
=
0
for all
k
k
k
.
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