Generated by SassMeister.com.

list-bordered-inner.html

  <ol class="bordered-inner bordered-inner-3-cols">
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>  
  </ol>

list-bordered-inner.scss

// ----
// Sass (v3.3.10)
// Compass (v1.0.0.alpha.20)
// ----

ol {
  width: 600px;

  li {
    width: 200px;
    height: 100px;
    box-sizing: border-box;
  }
}

.bordered-inner {
  
    &:after {
      content: "";
      display: table;
      clear: both;
    }
    
  
    li {
      box-sizing: border-box;
      float: left;
      border-width: 0;
      
      border-color: black;
      border-style: solid;
      border-right-width: 1px;
      border-bottom-width: 1px;
    }
    
}

@for $i from 2 to 10 {
  
  .bordered-inner-#{$i}-cols {

    li {
      &:nth-child(#{$i}n) {
        border-right:none;
      }
      &:nth-last-child(-n+#{$i}) {
        border-bottom: none;
      }
    }

  }

}