# How to read/interpret this equation

by TheMarksman
 HW Helper P: 1,391 That's not a matrix, it's a standard notation for a binomial coefficient: $$\left(\begin{array}{c}{n \\ k}\end{array}\right) = _nC_k = \frac{n!}{k!(n-k)!}$$
What matrix? Is $\tau$ a matrix? Because ${n \choose k}$ is not a matrix.