If you have only these two fix scenario.Then you can try Jeff's Tally table as mentioned below.

--===== Do this in a nice safe place that everyone has

-- (You can build a permanent one in any database)

USE TempDB;

IF OBJECT_ID('TempDB..Tally','U') IS NOT NULL

DROP TABLE Tally;

GO

--===================================================================

-- Create a Tally table from 1 to 1000 (you can increase this number as per your requirement)

--===================================================================

--===== Create and populate the Tally table on the fly.

SELECT TOP 1000

IDENTITY(INT,1,1) AS N

INTO dbo.Tally

FROM Master.sys.ALL_Columns ac1

CROSS JOIN Master.sys.ALL_Columns ac2

;

--===== Add a CLUSTERED Primary Key to maximize performance

ALTER TABLE dbo.Tally

ADD CONSTRAINT PK_Tally_N

PRIMARY KEY CLUSTERED (N) WITH FILLFACTOR = 100

;

--===== Allow the general public to use it

GRANT SELECT ON dbo.Tally TO PUBLIC

;

GO

------ Now move to your query

SELECT 'AA' + RIGHT('00'+ CONVERT(VARCHAR,N),3) + 'A0' AS NUM

FROM tempdb.dbo.Tally

WHERE N < 1000

Likewise you can try out the second pattern on your own 🙂