I have tried evaluating this series $$\sum_{n=1}^{\infty}\frac{H_{n}^3}{(n+1)3^n} $$ using some methods but it's seems to me that it is very hard. However, I noticed that the series converges faster than the Riemann series. **My question here is:** Is there some mathematical technique for evaluating the above series? **Note:** Here, $H_n$ denotes the harmonic numbers. Thank you for any help.