the answer will be 21
This is the series of square numbers, (16= 4*4). The next number is 5*5=25.
The next number is 25 but there are the sequence is infinite so there can be no end to the sequence.
it should already have come out
There is no specific number. It all depends on what shows are good. Should a bunch of new series come out on year that nobody likes, many new series will come out to follow. That year, there would be many TV series. However, a year that has many great TV series that everybody watches would have little new series, thus having less TV series that year.