<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("p:nth-child(3n+2)").css("background-color", "yellow");
});
</script>
</head>
<body>
<p>The p:nth-child(3n+2) selects each 3rd paragraph, starting at the 2nd child element.
<div style="border:1px solid;">
<span>This is a span element</span>
<p>The first paragraph (and the second child in div).</p>
<p>The second paragraph.</p>
<p>The third paragraph.</p>
<p>The fourth paragraph.</p>
<p>The fifth paragraph.</p>
<p>The sixth paragraph.</p>
<p>The seventh paragraph.</p>
<p>The eight paragraph.</p>
</div><br>
</body>
</html>