Byoung Chan Lee (이병찬)

Prove that if x is a real number such that \(0<x\le \frac12\), then x can be represented as an infinite sum 

\(\displaystyle x=\sum_{k=1}^\infty \frac{1}{n_k}\),

where each \(n_k\) is an integer such that \(\frac{n_{k+1}}{n_k}\in \{3,4,5,6,8,9\}\).

The best solution was submitted by Byoung Chan Lee (이병찬), 수리과학과 2007학번. Congratulations! 

Click here for his Solution of Problem 2008-2.