MathDB
Problems
Contests
National and Regional Contests
Israel Contests
Israel Team Selection Test
2025 Israel TST
P1
P1
Part of
2025 Israel TST
Problems
(1)
Rational sequence reaches 1
Source: 2025 Israel TST Test 1 P1
10/28/2024
A sequence starts at some rational number
x
1
>
1
x_1>1
x
1
>
1
, and is subsequently defined using the recurrence relation
x
n
+
1
=
x
n
⋅
n
⌊
x
n
⋅
n
⌋
x_{n+1}=\frac{x_n\cdot n}{\lfloor x_n\cdot n\rfloor }
x
n
+
1
=
⌊
x
n
⋅
n
⌋
x
n
⋅
n
Show that
k
>
0
k>0
k
>
0
exists with
x
k
=
1
x_k=1
x
k
=
1
.
number theory
algebra
Sequence