The puzzle is not "Find a rule that matches everything you tested". It's figure out what rule they are using. It may be true that there are multiple ways to state the rule, such as "x_2 >= x_1 + 1 and x_3 is >= x_1 + 2" but they are equivalent.

Try the sequence: 0,0,0. It would give "yes" for (x,2x,4x), but the actual rule gives it "no".