The binomial coefficients for $(1 + x)^n$ are:
\[
\binom{n}{0}, \binom{n}{1}, \ldots, \binom{n}{n}.
\]
The product $P_n = \prod_{k=0}^n \binom{n}{k}$.
Using known formula or induction:
\[
\frac{P_{n+1}}{P_n} = \frac{(n+1)^{n+1}}{(n+1)!}.
\]
Hence, option (4) is correct.