title: LESS - use nth-child variable in string
body: <p>Surely there's a way to rewrite the following in LESS?</p>
  
  <pre><code>#bg-slider{
  
  li:nth-child(1){
      background:url('../images/bg1.jpg');
  }
  
  li:nth-child(2){
      background:url('../images/bg2.jpg');
  }
  
  li:nth-child(3){
      background:url('../images/bg3.jpg');
  }
  
  }
  </code></pre>
  
  <p>I've tried:</p>
  
  <pre><code>.bg-image (@slide) {
    background:url('../images/bg@{slide}.jpg');
  }
  
  #bg-slider{
  li:nth-child(n){
      .bg-image(n);
  }
  }
  </code></pre>
  
  <p>But that just gives '../images/bgn.jpg' for all li's.</p>