<p>若级数<img src="https://learnfile.20230611.cn/learnAppQuestion/54/02/5402c922e98784a2c881c06dd74896d6.jpg" style="width: 100%;height: auto;">的前n项和<img src="https://learnfile.20230611.cn/learnAppQuestion/8f/56/8f56e324308b74c0bfc05f730648b45e.jpg" sty