Solution (source code)

= Solution

The sum of the sizes of the partitions at the next level of the <quotient tower of a partition> is
$$
w_e(\lambda)=\frac{|\lambda|-|C_e(\lambda)|}{e}
\leq\frac{|\lambda|}{e}.
$$
For $e>1$, repeated passage to a quotient therefore makes every branch empty after finitely many levels. For $e=1$, the core is empty and $Q_1(\lambda)=(\lambda)$, so a nonempty partition repeats forever. Thus the tower has finite depth exactly when $e>1$ or $\lambda$ is empty.