# How can I write the symbol of ”combinations of n things taken k at a time”?

## I am familiar with the notation ${C}_{n}^{k}$, but I noticed that most people on Socratic use this kind of notation:

Jun 3, 2015

Here's how that would look

• Without the hashtags

( (n), (k) )

• With the hashtags

$\left(\begin{matrix}n \\ k\end{matrix}\right)$

It's the same notation you use to write matrices

$\left(\begin{matrix}1 & 2 & 3 \\ 4 & 5 & 6\end{matrix}\right)$

More examples here:

http://socratic.org/questions/how-to-write-matrices-on-socratic?source=search