title: Calculate count of permutations in array without repetition by Javascript
body: <p>First I have an array, like this:</p>
  
  <pre><code>var arr = [[2,3,4,5,6,7,8,9,10],
             [3,4,5,6,7,8,9,10,11],
             [4,5,6,7,8,9,10,11,12]]
  </code></pre>
  
  <p>It is not necessarily should be this array, it could be any other, it is just example. So I need to know the count of all possible permutations, something like this:</p>
  
  <pre><code>2,3,4
  2,3,5
  ...
  2,3,12
  
  2,4,5
  2,4,6
  ...
  2,4,12
  
  ...
  10,11,12
  </code></pre>
  
  <p>It is not simple permutations, as I understand. And also I don't need all this combination, I just need their count, may be exist formula or something like this. In this example I know that answer is 165. Thank you</p>