New combinatorial formula for modified Hall-Littlewood polynomials

We obtain new combinatorial formulae for modified Hall--Littlewood polynomials, for matrix elements of the transition matrix between the elementary symmetric functions and Hall-Littlewood's ones, and for the number of rational points over the finite field of unipotent partial flag variety. The definitions and examples of generalized mahonian statistic on the set of transport matrices and dual mahonian statistic on the set of transport (0,1)-matrices are given. We also review known q-analogues of Littlewood-Richardson numbers and consider their possible generalizations. Several conjectures about multinomial fermionic formulae for homogeneous unrestricted one dimensional sums and generalized Kostka-Foulkes polynomials are formulated. Finally we suggest two parameters deformations of polynomials $P_{\lambda\mu}(t)$ and one dimensional sums.