<image>A sequence of figures is composed of parallelograms of the same size arranged according to a certain pattern. In the 1st figure, there are a total of 6 parallelograms. In the 2nd figure, there are a total of 18 parallelograms. In the 3rd figure, there are a total of 36 parallelograms. ..., then the number of parallelograms in the nth figure is ____.
