  Using equivariant cohomology theory, Naruse obtained a hook length formula
for the number of standard Young tableaux of skew shape $\lambda/\mu$. Morales,
Pak and Panova found two $q$-analogues of Naruse's formula respectively by
counting semistandard Young tableaux of shape $\lambda/\mu$ and reverse plane
partitions of shape $\lambda/\mu$. When $\lambda$ and $\mu$ are both staircase
shape partitions, Morales, Pak and Panova conjectured that the generating
function of reverse plane partitions of shape $\lambda/ \mu$ can be expressed
as a determinant whose entries are related to $q$-analogues of the Euler
numbers. The objective of this paper is to prove this conjecture.
