The Sequence class only has _initalValue which means that when a sequence is altered (by DROP and CREATE) the existing last_value, aka existing sequence ID is lost and the first attempt on flushing a new record results in a pkey exception.
This result in the sequence counter starting all over.
This can be handled by setting _initalValue to whatever is the last sequence value but since it is also used for setting MINVALUE this may not be a good idea. They should be split.
Not sure what name to use, last_value is from postgresql but I'm sure others use different names.