The USPTO is now using series code 13 for patent application serial numbers assigned from the end of 2010 forward. The first application in the series, 13/000,001, was published on May 26, 2011 (2011/0121738A1). Series code 12 was in use from December 2007 to early 2011.
I'm the librarian for research services in the Engineering and Science Library at Queen's University in Kingston, Ontario. I've been working with patent information since 1991, including seven years at the U.S. Patent and Trademark Office. I believe that the dissemination of patent information is a public good and should be promoted, especially in the education of science and engineering students.