Here "generation" refers to the people in it. AT: "The people living at this time are evil people. They seek ... to them" or "You people living at this time are evil people. You seek ... to you"
The information about what kind of sign it seeks can be made explicit. AT: "It wants me to perform a miracle as proof that I have come from God" (See: [[rc://en/ta/man/translate/figs-explicit]])