|   | 1 |  initial version  | 
As the other contributors have said, you can simply use python.
Just another version:
a=[[1,3],[4,5,6],[2,3,4,6,7],[1,3]]
givememaxlen=lambda x: max([len(i) for i in x]);
print(givememaxlen(a))
 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.