I would like to give you a small example to use the sequence.currval and sequence.nextval

create sequence seq_name

start with 1

minvalue 1

maxvalue 999

increment by 1

insert into table_name (sno name) values (seqname.nextval 'abc');

select seqname.currval from dual

select <sequencename>.nextval from dual;

select <sequencename>.currval from dual;

or

select * from user_sequences where sequence_name <sequencename>;

here last_number is your currval and last_number + increment_by is your nextval