Math formula in post not display after save

Let’s try here to see.

\left. \begin{array}{l} \text{if $n$ is even:}&n/2\\ \text{if $n$ is odd:}&3n+1 \end{array} \right\} =f(n)

I can’t reproduce the issue here.
Would you be okay to share your forum URL here (or by PM if you prefer)?