We know that a K-map is used to represent and simplify a boolean function. Given 'n' no. of boolean variables, number of cells in the K-map is 2^n. Now each cell has two options. Either 1(True) or 0(False) [in case of SOP]. Different combinations of cells each having value=1 will give generate different functions (which later can be simplified but that is not our concern here). So in that way total number of functions will be 2^(2^n).