title: Creating all possible combinations from multiple sets
body: <p>I've limited knowledge in maths so pardon the terms if i'm mistaken.
  I need to create all possible combinations from multiple sets with at least 1 item included from that set.</p>
  
  <pre><code> - SetA: [1, 2, 3, 4, 5, 6, 7] 
   - SetB: [a, b, c, d] 
   - SetC: [!, @, #, $, %]
  </code></pre>
  
  <p>Example Output:</p>
  
  <pre><code> - [1,a,!]
   - [1,2,a,c,@]
   - [1,2,3,4,5,6,7,a,b,c,d,!,@,#,$,%]
  </code></pre>
  
  <p>Is there a specific combination formula for this since i can only come up with nested loops and i'm not sure if it is even correct.</p>