Howtoselectparentparentofelement

I am using SASS, I have got 10 elements like this:

<div class="parent">
    <div class="parent__child"></div>
</div>

My sass is:

.parent
  some sass

  &:nth-of-type(2n)
    some sass

    ?????

  &__child
    background: green

What I want

CSS:

.parent:nth-of-type(2n) .parent__child{ some css }

SASS: ???

How can I do this? Thank you!