\( J_\alpha(x) = \sum\limits_{m=0}^\infty \frac{(-1)^m}{m! + 1}{\left({\frac{x}{2}}\right)}^{2 m + \alpha} \)
\( \sum\limits_{i = 0} ^ {n} \sum\limits_{j = 0}^{m} gcd(i, j) == 1 \)
\( \lfloor \frac{2}{n} \rfloor \)
\( a_{1} \ a_{2} \ \ \ \ \ \ \ \ \ \ \ a_{3}\)
\( a^1 a^2 a^3 \)
原文：http://www.cnblogs.com/sxprovence/p/5396814.html