"CREATE SEQUENCE "RECORD_ID" MINVALUE
1 MAXVALUE 999999999999999999999999999
INCREMENT BY 1 START WITH 1000 CACHE 20
NOORDER NOCYCLE " If we use the command as
RecordId,Nextval will fetch the incremented value as
1001 and RecordId,Currval will fetch 1000, Once we use NextVal command, sequence will internally incremented and it will maintain uniqueness to supply next number, Using Apex ObJect Browser, creation of sequence is as follows:
Create SEQUENCE
Click CREATE in ObJect Browser 
select the
Sequence ObJect
Type Voucher-seq in Sequence Name
Give minimum value as 1
Give Maximum value as
9999999999999999
Give increment value as 1 CLICK NEXT
Under Sequence window CLICK CREATE