Compass @for and iteration

Question

I'm trying to do a menu with 4 sub levels. I'd like to use a @for method.

I want to have

nav ul > li {....}
nav ul > li  ul > li {....}
nav ul > li  ul > li  ul > li {....}
nav ul > li  ul > li  ul > li ul > li {....}

Then i tried

 nav {
    @for $i from 0 through 3 {
        & ul {
            & li {
                padding-left: 20px*$i;
            }
        }
    }
 }   

The result is I only have 1 level.

Thanx to help me

Answer 1

And here is the for

$selectors: ('& ul > li', '& ul > li ul > li', '& ul > li ul > li ul > li', '& ul > li ul > li ul > li  ul > li')

nav
  @for $i from 1 through 4
    #{nth($selectors, $i)}
      padding-left: 200px * $i

spits out the same

/* line 5, style.sass */
nav ul > li {
  padding-left: 200px;
}
/* line 5, style.sass */
nav ul > li ul > li {
  padding-left: 400px;
}
/* line 5, style.sass */
nav ul > li ul > li ul > li {
  padding-left: 600px;
}
/* line 5, style.sass */
nav ul > li ul > li ul > li ul > li {
  padding-left: 800px;
}