Some comments on "On the generating function for intervals in Young's lattice" by Azam and Richmond

Azam and Richmond arXiv:2107.09149 obtained a recursion for the generating function of $P_{\lambda }(y)$, itself a generating function enumerating by length partitions in the lower ideal $[0,\lambda ]$ in the Young lattice. We show that this recursion can be extended to a multi-graded version. This is done by interpreting the original problem as enumerating plane partitions with two rows. We can then use the well-developed theory of lattice points in polyhedral cones to determine some properties of the generating function. We also relate Azam and Richmond’s result to those obtained by Andrews and Paule using MacMahons Omega-operator.