Question: I have been reading this [article](https://css-tricks.com/how-nth-child-works/) and it is pretty clear to me so far that something along the lines of: `ul li:nth-child(3n+3)` will select every 3rd `li` due to the fact that the "n" within the expression starts at zero and then represents a set of all positive integers; so n = 0, n = 1, n = 2, etc., which in the article I have linked goes on to indicate that indeed `:nth-child(3n+3)` is tantamount to (3x0)+3 which equals 3, (3x1)+3 equals 6 and so on. I have also seen similar CSS such as: `.some-selector:nth-child(1n); .some-selector:nth-child(2n);` 
What I glean from the examples from the aforementioned article leads me to posit that `.some-selector:nth-child(1n);` would equate to `.some-selector:nth-child(0);` but this also feels wrong to me. Can someone help me to better understand this? Thanks

Answer: 
Your feeling is correct, `:nth-child(1n)` does not equal `:nth-child(0)`. A selector with an expression like `:nth-child(1n)`, or actually `:nth-child(n)` which is the same would select all children. So apparently it wouldn't make much sense...

To understand which elements are going to be selected you have to give `n` incremental values starting from 0, as in the table in the article you linked, and all the values you get will be the indexes of the selected elements.

There are also some [:nth Testers](https://css-tricks.com/examples/nth-child-tester/) that will help you understand better.
`.block:nth-child(1n)` will target every element with the class `block` that is a multiple of 1

So it will result the exact same thing as `.block{...}`

```css
.block {
  height: 50px;
  width: 50px;
  background: dodgerblue;
  margin: 3px;
}

.block:nth-child(1n) {
  background: red;
}
```

```html
<div class="block">
</div>
<div class="block">
</div>
<div class="block">
</div>
```

If you want to select only the first one you can use the following

```css
body {
  display: flex;
  justify-content: space-around;
}

.block {
  height: 50px;
  width: 50px;
  background: dodgerblue;
  margin: 3px;
}

.first .block:nth-child(1) {
  background: red;
}

.second .block:nth-child(n+2) {
  background: red;
}
```

```html
<div class="first">
  Target only the first one
  <div class="block">
  </div>
  <div class="block">
  </div>
  <div class="block">
  </div>
</div>

<div class="second">
  Target every block except for the first one
  <div class="block">
  </div>
  <div class="block">
  </div>
  <div class="block">
  </div>
</div>
```