<image>When \( n \) is equal to \( 1 \), \( 2 \), \( 3 \)..., the figures composed of white small squares and black small squares are shown in the picture. Then the total number of white small squares and black small squares in the \( n \)-th figure is equal to ______. (Express your answer in terms of \( n \), where \( n \) is a positive integer.)