Most of modern India, plus a good bit of what is now Pakistan, Bangladesh, and Burma.
I wonder about Ashoka’s empire — around 300 BC. What parts of India would have been populated? Most likely the Ganga-Jamuna river valley, Punjab and the coastlines. The interiors would remain non-Aryan for a long time yet and the furthest east would be Bengal.
That part ceded by Seleukus Nikator -- that was the ruler of one of the successor states after the death of Alexander the Great; I think that Ashoka's grandfather and predecessor Chandragupta Maurya was a boy when Alexander's army came through; Chandragupta was married to (among others) Seleukus Nikator's daughter, that swath of territory and the marriage cemented an alliance.
