Can sequences be replicated?
No, the best way to handle sequences, assuming you are using them as primary key values, is to concatenate then with something unique to the site. For example, use a sequence number concatenated with the database name, site name or something similar. One could also start the sequences at one site as odd numbers (1, 3, 5, etc) and the other site as even numbers (2, 4, 6 etc).