The given sequence is:
\[
a_{n} = \frac{n!}{(n+1)!} n^{2}
\]
Recall that \( (n+1)! = (n+1) \cdot n! \). Substitute this into the expression:
\[
a_{n} = \frac{n!}{(n+1) \cdot n!} n^{2}
\]
Step 2: Cancel out \( n! \)
The \( n! \) terms in the numerator and denominator cancel out:
\[
a_{n} = \frac{1}{n+1} n^{2}
\]