2 problems

Let $R_{n,k}(q,t)$ be the $(q,t)$-Schröder polynomial obtained by weighting little Schröder paths with the statistics defined above, and let $[m]_q$ and $[m]!_q$ denote the $q$-int…

Let $\operatorname{Cat}_{n,r}(q,t,z,w)$ and $\operatorname{Cat}'_{n,r}(q,t,z,w)$ be the refinements of the 4-variable Catalan polynomials obtained by summing over Dyck paths of ord…