title: creating this matrix in matlab
body: <p>Given </p>
  
  <pre><code>A=[a_1 a_2 a_3 ... a_n]
  </code></pre>
  
  <p>How to make this?</p>
  
  <pre><code>[a1 ... a100]
  [a2 ... a101]
  ...
  [an-100+1 ... an]
  </code></pre>
  
  <p>I want to not use for-loop here since I want to speed it up.
  Thank you.</p>