Posted by haifeng on 2011-06-21 18:22:12 last update 2011-06-21 18:22:12 | Edit | Answers (0)
\[
1-\frac{1}{2}+\frac{1}{4}-\frac{1}{5}+\frac{1}{7}-\frac{1}{8}+\frac{1}{10}-\frac{1}{11}+\cdots=\frac{\pi}{3\sqrt{3}}
\]
The two fomulae are attributed to Euler by Scharlau and Opolka
