Continuing the process, we arrive at the following formula w ( n , g ) = ∑ ∑ k 1 = 0 n ∑ ∑ k 2 = 0 n − − k 1 w ( n − − k 1 − − k 2 , g − − 2 ) = ∑ ∑ k 1 = 0 n ∑ ∑ k 2 = 0 n − − k 1 ⋯ ⋯ ∑ ∑ k g = 0 n − − ∑ ∑ j = 1 g − − 1 k j w ( n − − ∑ ∑ i = 1 g k i , 0 ) . Using the convention (7) 2 above, we obtain the formula