title: How to generate all subsets of a given size?
body: <p>Given some number n, and a subset size, I want to get all possible subsets of the specified size of the set {1, ..., n}.</p>
  
  <p>Expected result for for <code>n = 5</code> and <code>subsetSize = 4</code>:</p>
  
  <pre><code>{{1,2,3,4}, {1,2,3,5}, {1,3,4,5}, {1,2,4,5}, {2,3,4,5}}
  </code></pre>
  
  <p>(that would be a <code>List&lt;List&lt;int&gt;&gt;</code>)</p>
  
  <p>That means I need to get (subsetSize choose n) subsets (Newton's symbol).</p>
  
  <p>Any idea for an algorithm that could find me such a list of lists of integers? I'm implementing it in C#, if that matters.</p>