Summation calculus: $\sum_{k=1}^n \frac{2^{2^{k-1}}}{1-2^{2^k}}$ How can I solve this?
$$\sum_{k=1}^n \frac{2^{2^{k-1}}}{1-2^{2^k}}$$
Actually I tried many direction, but failed.
Please give me some right direction.

$$\sum_{k=1}^n \frac{2^{2^{k-1}}}{1-2^{2^k}} = \sum_{k=1}^n \frac{2^{2^{k-1}}}{(1-2^{2^{k-1}})(1+2^{2^{k-1}})}=\cdots$$  

Let $$S = \sum_{k=1}^n \frac{2^{2^{k-1}}}{1-2^{2^k}} = \sum^{n}_{k=1}\bigg[\frac{(1+2^{2^{k-1}})-1}{1-2^{2^k}}\bigg] = \sum^{n}_{k=1}\bigg[\frac{1}{1-2^{2^{k-1}}}-\frac{1}{1-2^{2^k}}\bigg]$$
which is nothing but Telescopic Sum
So $$S = -1-\frac{1}{1-2^{2^{n}}}$$
