File:Inclusion exclusion diagram.JPG

Summary
Counts of each region with progressively more terms used for n = 4. However, this picture does not show the general situation, as (with one labeling) it assumes that D is disjoint from the part of A that avoids B and C. In fact, the general situation cannot be depicted with a Venn diagram.

Author: Myself, Jobba III Esq.

(Please feel free to improve this diagram, it's not that precise or necessarily clear - it's a first draft and I'm a little lazy..)