mrijet:
This behavor is by design. The autonumber was and is not intended to be used as a sequential numbering system. The purpose of this datatype is to provide a unique, unrelated, record-id for use as a primary key.
If you need a sequential number, there are several threads covering this topic (for example
this thread covers a method for sequential with year looping; however, we do have simpler "check" number solutions in the forum too :-) ) If you have something more specific and an example of your work-flow, someone here can help steer you in the right direction.
Aftab Ahmad
Removing the [indexed no duplicates] is highly inadvisable unless one is aware of the consequences of such an act on the autonumber field.