Syntax diagram Ex induction mathematical chapter class
c# - What's the difference between ^([1-9]{1,2},){4}[1-9]{1,2}$ and ([1

Question 11 - Prove 1/1.2.3 + 1/2.3.4 + 1/3.4.5 .. + 1/n(n+1)(n+2)
![c# - What's the difference between ^([1-9]{1,2},){4}[1-9]{1,2}$ and ([1](https://i2.wp.com/i.stack.imgur.com/NNy75.png)
c# - What's the difference between ^([1-9]{1,2},){4}[1-9]{1,2}$ and ([1