Series LLC in Pennsylvania
Technically you could have a DE Series LLC operating in Pennsylvania, however since Pennsylvania does not have Series LLC law I am not sure how each Series of DE LLC would be treated in Pennsylvania courts.
It is possible that each series will be treated as a separate entity (in which case you would need to register each series as a separate foreign entity in PA), or it might fold all the entities into one, in which case you loose the advantage of having Series LLC to begin with. In other words, it doesn't seem like there is much advantage in forming DE Series LLC for a business in Pennsylvania.
I would, of course, urge you to consult a business attorney that specializes in Series LLC to get a better idea of what you can and cannot do with this type of business entity.