Problems with list_authors

Masers for the W(P)orld,

I could use some help with the list_authors and wp_list_authours tags. I’ve tried both of the code snippetts below, but I still get the admin included in the list

<ul>
<?php list_authors(TRUE, TRUE, TRUE, TRUE);???>
</ul>

or

<?php wp_list_authors('optioncount=1&show_fullname=1');???>

This second bit of code was lifted straight from the codex. Am I doing something wrong?

Here’s a second question: What would I need to do to take the list generated in the code above and filter out authors who haven’t posted in the past seven days?

Thanks!