According to the FICS Games Database there are currently 1,525 "computers stored". Such accounts are indicated by a "(C)" after the username. However, this suffix does not seem to be recorded in the database.
There is an outdated list here: https://www.freechess.org/Help/HelpFiles/computer_list.html.
Where do I find a recent, complete list of the usernames of all 1525 "computers stored"?