Sequences problem

Hello everybody, I have a question related with sequences.............

When I init a sesion with my db, if a do the next sentence:

SELECT currval('pagos_id_pago_seq');

return this:
ERROR: the relation doesn't exist
(or somethimg like that, because the message is in spanish)

but if I do first,

SELECT nextval('pagos_id_pago_seq');

and then
SELECT currval('pagos_id_pago_seq'); it success, returns the
current sequence value, it is possible to indicate that the sequence is
already started and in the value 4567 but I need first to now the
current value before the next, how can I do?

Thanks in advanced