Lattice equations arising from discrete Painleve 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 Painleve systems, on which quad-equations of ABS type appear. In particular, we consider the $A_5^{(1)}$- and $A_6^{(1)}$-surface $q$-Painleve systems corresponding affine Weyl group symmetries are of $(A_2+A_1)^{(1)}$- and $(A_1+A_1)^{(1)}$-types, respectively.