通项公式a(n) = 1 + 2 + 2^2 + ...+ 2^(n-1) = 2^n - 1,n = 1,2,...S(n) = a(1) + a(2) + ...+ a(n)= 2^1 - 1 + 2^2 - 1 + ...+ 2^n - 1= 2[1 + 2 + ...+ 2^(n-1)] - n= 2[2^n - 1] - n= 2^(n+1) - n - 2,(n = 1,2,....