Logic behind triple loops

Hi

I am new in triple loops and trying to find a way to automate the generation of these numbers:

11000  11001  21001        
11001  21001  31001          
11002  31001  41001          
11003  11002  21002          
11004  21002  31002          
11005  31002  41002          
11006  11003  21003          
11007  21003  31003
11008  31003  41003          
11009  11004  21004          
11010  21004  31004          
11011  31004  41004        
11012  11005  21005

[Rik]

If you explain what pattern you're looking for we might be able to help you. This is not your first question, you should be aware of how to make it easy for people to help you by now.