Generated by SassMeister.com.

SassMeister-input-HTML.html

<ul>
  <li class="item-1">item 1</li>
  <li class="item-2">item 2</li>
  <li class="item-3">item 3</li>
</ul>

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

@for $i from 1 through 3{
  .item-#{$i}{
    padding-left:20px*$i;
    background:#424242*$i;
  }
}

SassMeister-output.css

.item-1 {
  padding-left: 20px;
  background: #424242;
}

.item-2 {
  padding-left: 40px;
  background: #848484;
}

.item-3 {
  padding-left: 60px;
  background: #c6c6c6;
}

SassMeister-rendered.html

<ul>
  <li class="item-1">item 1</li>
  <li class="item-2">item 2</li>
  <li class="item-3">item 3</li>
</ul>