Define a sequence $(C\_n)$ by $C\_0=1$, $C\_1=1$, and $C\_{n+1} = \sum\_{r=0}^n C\_r C\_{n-r}$ for $n\geq 2$. What is the simplest explicit formula for $C\_n$?



What is the simplest non-recursive formulation for the following recursive function?
You want [Catalan number](http://en.wikipedia.org/wiki/Catalan_number)


