The coefficients are $\binom{n}{k}$ for $0\le k\le n$. The maximum is in the middle. If $n$ is even then the max is at $\frac{n}{2}$. If $n$ is odd, it is max at a pair at $\frac{n-1}{2}$ and $\frac{n+1}{2}$.

You can work it out yourself. Be careful, $k$ starts at $0$.