Solution (source code)

= Solution

A two-runner <partition abacus> gives
$$
Q_2(3,1)=((2),\varnothing),
\qquad
Q_2(2)=(\varnothing,(1)),
$$
and the 2-quotients of $(1)$ and $\varnothing$ are empty. Thus the <two-quotient tower of the partition three-one> has nonempty levels
$$
\boxed{
TQ_2(3,1)_0=((3,1)),
\quad TQ_2(3,1)_1=((2),\varnothing),
\quad TQ_2(3,1)_2=(\varnothing,(1),\varnothing,\varnothing).}
$$