sequences and series - Evaluate $sum_{n=1}^{infty }ln left (frac{7^n+1}{7^n} right )$

Evaluate $\sum_{n=1}^{\infty }\ln \left (\frac{7^n+1}{7^n} \right )$ .

Found this question on Art of Problem Solving. It was stuck in the "solved" section, but I couldn't find a solution, and I myself am stumped.

Apparently it could also be simplified to $\sum_{k=0}^{\infty }\frac{\left ( -1 \right )^{k+1}}{k\left ( 7^{k}-1 \right )}$ , but I don't follow this either.