Serial sequence name when table/column name in uppercase

Hello,

How do I get the sequence name for a serial/bigserial column, of a table
and/or column name is created with uppercase letters?

test1=> create table "TAB13" ( "PKEY" BIGSERIAL, "NAME" VARCHAR(50) );
CREATE TABLE

test1=> select pg_get_serial_sequence(current_schema||'.tab13','pkey');
ERROR:  relation "public.tab13" does not exist

test1=> select pg_get_serial_sequence(current_schema||'.TAB13','PKEY');
ERROR:  relation "public.tab13" does not exist

test1=> select * from "TAB13";
  PKEY | NAME
------+------
(0 rows)



Seb