A new word is becoming more and more popular on the Internet in China - but no one knows quite what it means. The word "duang" is so new that you can't even find it in the Chinese dictionary. But it has already spread(传播) like fire on the Chinese Internet, appearing more than 8,000,000 times on Weibo, where 15,000 users had more than 312,000 discussions. On Baidu, it has been looked up almost 600,000 times. But what does it mean?

    "Everyone's duang-ing and I still don't know what it means! Looks like I'd better go back to school now," said Weibo user Fahmida.

    Another user asked: "Have you duang-ed today? My mind is full of duang duang duang."

    "To duang or not to duang, that is the question," wrote user Beatrice.

    "Duang" seems to be imitating (模仿) a sound. It all seems to have started with Hong Kong action star Jackie Chan, who in 2004 appeared in a shampoo ad (洗发水广告) where he used the sound "duang" to describe his soft and black hair. The word came to people again recently(最近) after Chan posted it on his Weibo page. Thousands of users then began to visit Chan's Weibo page with comments (评论).

    The word seems to have many different meanings, and there's no perfect (完美的) Chinese meaning for it, but you could use it to give emphasis (强调) to the word that follows it. A kid might be "duang cute", for example.

数列{a_n}满足a₁=1，且a_n+1-a_n=n+1(n$\in$N^*)，则数列{$\frac{1}{a_n}$}的前10项和为  ____   。