I found the URL http://www.musicbrainz.org/showartist.html?artistid=152517 in an old note, but the link doesn't map to anything, it just returns a 404. The link should redirect me to an artist it refers to or point me to the correct search.

It is important for long running projects to redirect all their old URL structures to their new ones, all kinds of links are floating around who knows where! 😉