Recently, I’ve met a problem like this when I deploying my blog. hexo d gets error.

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ssh: connect to host github.com port 22: Connection timed out
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
FATAL Something's wrong. Maybe you can find the solution here: https://hexo.io/docs/troubleshooting.html
Error: Spawn failed
    at ChildProcess.<anonymous> (D:\Study\Blog\node_modules\hexo-util\lib\spawn.js:52:19)
    at ChildProcess.emit (events.js:198:13)
    at ChildProcess.cp.emit (D:\Study\Blog\node_modules\cross-spawn\lib\enoent.js:40:29)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:248:12)

When this occurs, usually you just need to deploy it again in good internet condition. This is just your internet doesn’t work well, at least for me always.

Here are some sorting ways and I use many data to test and compare. Just to illustrate the property of each algorithm.

第六章 数理统计的基本概念

一、随机样本

（1）总体与个体

​ a. 一批灯泡的全体组成一个总体，其中每一个灯泡都是一个个体。

​ b. 一个随机变量X或其相应的分布函数$F(x)$成为一个总体。

第五章 大数定律和中心极限定理

一、*大数定律

（1）切比雪夫不等式

​ $X$有数学期望$E(X)=\mu,D(X=\sigma^2)$, 则对任意正整数$\varepsilon$

​ $P{\left| x - \mu \right| \geq \varepsilon } \leq \frac{\sigma ^2}{\varepsilon ^ 2}$

​ $P{\left| x - \mu \right| < \varepsilon } \geq 1-\frac{\sigma ^2}{\varepsilon ^ 2}$

第四章 随机变量的数字特征

一、数学期望

1. 离散型

   $$E(X)=\sum_{k=1}^{\infty} x_{k} p_{k}$$

Story of Cow

There is a cow that gives birth to a heifer at the beginning of each year. Each heifer starts in the fourth year and a heifer is born at the beginning of each year. Please program how many cows will there be in year n?