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Putnam
1958 November Putnam
A7
A7
Part of
1958 November Putnam
Problems
(1)
Putnam 1958 November A7
Source: Putnam 1958 November
7/19/2022
Let
a
a
a
and
b
b
b
be relatively prime positive integers,
b
b
b
even. For each positive integer
q
q
q
, let
p
=
p
(
q
)
p=p(q)
p
=
p
(
q
)
be chosen so that
∣
p
q
−
a
b
∣
\left| \frac{p}{q} - \frac{a}{b} \right|
q
p
−
b
a
is a minimum. Prove that
lim
n
→
∞
∑
q
=
1
n
q
∣
p
q
−
a
b
∣
n
=
1
4
.
\lim_{n \to \infty} \sum_{q=1 }^{n} \frac{ q\left| \frac{p}{q} - \frac{a}{b} \right|}{n} = \frac{1}{4}.
n
→
∞
lim
q
=
1
∑
n
n
q
q
p
−
b
a
=
4
1
.
Putnam
number theory
relatively prime