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2018 PUMaC Algebra A3
2018 PUMaC Algebra A3
Source:
November 25, 2018
PuMAC
algebra
Problem Statement
Let
x
0
,
x
1
,
…
x_0, x_1, \ldots
x
0
,
x
1
,
…
be a sequence of real numbers such that
x
n
=
1
+
x
n
−
1
x
n
−
2
x_n = \frac{1 + x_{n -1}}{x_{n - 2}}
x
n
=
x
n
−
2
1
+
x
n
−
1
for
n
≥
2
n \geq 2
n
≥
2
. Find the number of ordered pairs of positive integers
(
x
0
,
x
1
)
(x_0, x_1)
(
x
0
,
x
1
)
such that the sequence gives
x
2018
=
1
1000
x_{2018} = \frac{1}{1000}
x
2018
=
1000
1
.
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