Dan je skup

. Neka su

i

prirodni brojevi takvi da vrijedi

za sve

. Odredi najveću moguću vrijednost od

.
Given set

.Let

and

natural numbers such that

for all

. Find the greatest value of

.
[lang=hr]
Dan je skup $S = \{ xy\left( {x + y} \right)\; |\; x,y \in \mathbb{N}\}$. Neka su $a$ i $n$ prirodni brojevi takvi da vrijedi $a+2^k\in S$ za sve $k=1,2,3,...,n$. Odredi najveću moguću vrijednost od $n$.
[/lang]
[lang=en]
Given set $S = \{ xy\left( {x + y} \right)\; |\; x,y \in \mathbb{N}\}$.Let $a$ and $n$ natural numbers such that $a+2^k\in S$ for all $k=1,2,3,...,n$. Find the greatest value of $n$.
[/lang]