|   | 1 |  initial version  | 
See trac ticket 22908 for an implementation in Sage. I am adding a confirmed_bug tag (which will become fixed_bug once this will be merged).
 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.