IMO Shortlist 1992 problem 14
Dodao/la:
arhiva2. travnja 2012. For any positive integer
define
as greatest odd divisor of
and
Construct the sequence
Show that the number 1992 appears in this sequence, determine the least
such that
and determine whether
is unique.
%V0
For any positive integer $x$ define $g(x)$ as greatest odd divisor of $x,$ and $$f(x) =\begin{cases}\frac{x}{2}+\frac{x}{g(x)}&\text{if\ \(x\) is even},\\ 2^{\frac{x+1}{2}}&\text{if\ \(x\) is odd}.\end{cases}$$
Construct the sequence $x_1 = 1, x_{n + 1} = f(x_n).$ Show that the number 1992 appears in this sequence, determine the least $n$ such that $x_n = 1992,$ and determine whether $n$ is unique.
Izvor: Međunarodna matematička olimpijada, shortlist 1992