IMO Shortlist 1994 problem N6
Dodao/la:
arhiva2. travnja 2012. Define the sequence
as follows.
and
are coprime positive integers and
. Show that for every
there is an
such that
divides
. Is it true that
must divide
for some
?
%V0
Define the sequence $a_1, a_2, a_3, ...$ as follows. $a_1$ and $a_2$ are coprime positive integers and $a_{n + 2} = a_{n + 1}a_n + 1$. Show that for every $m > 1$ there is an $n > m$ such that $a_m^m$ divides $a_n^n$. Is it true that $a_1$ must divide $a_n^n$ for some $n > 1$?
Izvor: Međunarodna matematička olimpijada, shortlist 1994