Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
写出 a_n = (2n)/(n^2+1) 的前5项。
写出 a_n = (2n)/(n^2+1) 的前5项。
Natural Language
Math Input
Extended Keyboard
