https://s0.wp.com/latex.php?latex=%5Cdisplaystyle+E_n+%3D+%5Cleft%5C%7B1%2C+x%5E%7B%28p%5En%29%7D%2C+x%5E%7B%282p%5En%29%7D%2C+%5Cdots%2C+x%5E%7B%28+%28p-1%29p%5En%29%7D%5Cright%5C%7D+&bg=ffffff&fg=000000&s=0&c=20201002