Hi 'Ramarren', thanks a lot for your comment.
It's quite new for me that there exist so useful packages in CL.
I am working on some hard problem intersecting fields like Number Theory, Algebra and Combinatorics. I have chosen LISP because of its power of expression (which is still difficult for me to understand and use) and compact, elegant formulas which remind me mathematical formulas. Most important for me is to understand algorithms after some period of time needed for preparing theoretical background which means long months of delays.
The SERIES package seems to be exceptionally valuable for me, could you please reference some other packages that can help in my work?