How to number each output with a link?

Overall what I’m trying to do is list the number of attachments (1, 2, etc) for each post on a page. When you click on a number, it will change the image. Pretty much like a slideshow. How would I go about adding the numbers in my loop or could this be better solved via jQuery?

Code (so far):

<?php
		if( function_exists( 'attachments_get_attachments' ) )
			{
			$attachments = attachments_get_attachments();
			$total_attachments = count( $attachments );
		if( $total_attachments ) : ?>
		<ul class="process">
			<?php for( $i=0; $i<$total_attachments; $i++ ) : ?>
			<li><a href="<?php echo $attachments[$i]['location']; ?>"></a></li>
			<?php endfor; ?>
		</ul>
			<?php endif; ?>
	<?php } ?>

Desired Output (in view source HTML):

<li><a href="https://domain.com/path/to/image1.png">1</a></li>
<li><a href="https://domain.com/path/to/image2.png">2</a></li>
<li><a href="https://domain.com/path/to/image3.png">3</a></li>