PLSQL - Nextval fault

Question

The following code:

Create a Trigger that creates a log record every time a product is changed.

CREATE OR REPLACE TRIGGER CREATE_LOG
AFTER UPDATE OR INSERT ON PRODUTO
FOR EACH ROW
BEGIN
INSERT INTO LOG VALUES (IDLOG.NEXTVAL,SYSDATE, 'Produto ' || 
cast(:NEW.IDPRODUTO as varchar(10)) || ' alterado' );
END;

It shows the following error :

Errors: TRIGGER CREATE_LOG Line/Col: 3/1 PL/SQL: SQL Statement Ignored Line/Col: 3/25 PL/SQL: ORA-02289: Sequence does not exist