serial

I created this table:

create table se (n  serial);

 Column |  Type      |                   Modifiers
---------+---------+------------------------------------------------
 n           | integer    | not null default nextval('se_n_seq'::regclass)

I inserted two record, later select, but column n (serial) no
auto-incremented
banco=# select * from se;
 n
---
 0
 0
(2 rows)

Why?
Thanks
Gustavo