Question Number 222592 by Tawa11 last updated on 30/Jun/25
![Σ_(n = 1) ^∞ (1/(cosh^4 [n ln((√2) + 1)]))](https://www.tinkutara.com/question/Q222592.png)
$$\underset{\mathrm{n}\:=\:\mathrm{1}} {\overset{\infty} {\sum}}\:\frac{\mathrm{1}}{\mathrm{cosh}^{\mathrm{4}} \left[\mathrm{n}\:\mathrm{ln}\left(\sqrt{\mathrm{2}}\:\:+\:\:\mathrm{1}\right)\right]} \\ $$