Lattice equations arising from discrete Painlev\'e systems (I):   $(A_2+A_1)^{(1)}$ and $(A_1+A_1')^{(1)}$ cases
  We introduce the concept of $\omega$-lattice, constructed from $\tau$ functions of Painlev\'e systems, on which quad-equations of ABS type appear. In particular, we consider the $A_5^{(1)}$- and $A_6^{(1)}$-surface $q$-Painlev\'e systems corresponding affine Weyl group symmetries are of $(A_2+A_1)^{(1)}$- and $(A_1+A_1)^{(1)}$-types, respectively. 
Nalini Joshi, Nobutaka Nakazono and Yang Shi
nlin.SI