Oracle 18c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

create table MASTER_RULE (VALUE varchar2(30))
insert into MASTER_RULE values ('A22')
1 rows affected

insert into MASTER_RULE values ('A16')
1 rows affected

insert into MASTER_RULE values ('A161')
1 rows affected

insert into MASTER_RULE values ('A15')
1 rows affected

SELECT * FROM MASTER_RULE WHERE substr(value, 2,length(value)-1) between 15 AND 19

VALUE

A16

A15

SELECT * FROM MASTER_RULE WHERE REGEXP_LIKE(value, 'A[1][5-9]{4}')