Many thanks for your time and help, Valery and Luc. I think my question is not clear :
So, the vector created was OK , but it didn't show the way you like it... is that it?
In that case, let me tell you:
It is very hard to control the shape of output of the symbolic processor.
I think my question should be : "How to create the Divided-Difference-Formulas-Schema in the vector ?" :