The series 2, 4, 8, could be followed by 7004.

The series 2, 4, 8, could obviously be followed by 16, but also by 10 or even 7004.
It's always possible to find a rule, a justification which allows a series to be continued by any number. It all depends on how complicated the rule is. So, any number can follow any series.
Reference: The Oxford Murders (2008)