\Big(1-\frac{1}{3}-\frac{1}{1\cdot3}\Big)+\Big(\frac{1}{3}-\frac{1}{5}-\frac{1}{3\cdot5}\Big)+\ldots+\Big(\frac{1}{2n-1}-\frac{1}{2n+1}-\frac{1}{(2n-1)(2n+1)}\Big)