1. How to prove $latex \sum_{n=1}^{\infty} {1/n^2} = \pi^2/6 $? Link (in Chinese), Link (in English)

2. How to prove $latex liminf_{n \to \infty} ~p_{n+1}-p_n < 7 \times 10^7 $, where $latex p_n $ is the $latex n$-th prime? Link, pdf, Career of Yitang Zhang (wiki)

At a time where money is the pursuit of many, what an amazing story.

3. HAKMEM (MIT, 1972)