Binomial Theorem

The number of terms in the expansion of $(x+y+z)^n$ is ______.

The coefficient of $x^3$ in the expansion of $(1+x)^5$ is ______.

The value of $\sum_{r=0}^{n} \binom{n}{r}$ is ______.

The value of $\binom{n}{r} + \binom{n}{r-1}$ is ______.