To rename a sequence, we should RENAME TO statement to rename it, but you have to login as the object's owner. For example:
SQL> show user
USER is "OE"
SQL> select object_type from user_objects where object_name = 'ORDERS_SEQ';
OBJECT_TYPE
-----------------------
SEQUENCE
SQL> rename orders_seq to order_id_seq;
Table renamed.
Although it returned "Table renamed.", the object is not necessarily a table.