@for

The @for rule, written @for <variable> from <expression> to <expression> { ... } or @for <variable> from <expression> through <expression> { ... }, counts up or down from one number (the result of the first expression) to another (the result of the second) and evaluates a block for each number in between. Each number along the way is assigned to the given variable name. If to is used, the final number is excluded; if through is used, it’s included.

  SCSS

  Sass

  CSS

      Playground
    SCSS Syntax$base-color: #036;

@for $i from 1 through 3 {
  ul:nth-child(3n + #{$i}) {
    background-color: lighten($base-color, $i * 5%);
  }
}

      Playground
    Sass Syntax$base-color: #036

@for $i from 1 through 3
  ul:nth-child(3n + #{$i})
    background-color: lighten($base-color, $i * 5%)

CSS Outputul:nth-child(3n+1) {
  background-color: rgb(0, 63.75, 127.5);
}

ul:nth-child(3n+2) {
  background-color: rgb(0, 76.5, 153);
}

ul:nth-child(3n+3) {
  background-color: rgb(0, 89.25, 178.5);
}