a query to generate 5 random DNA sequences that are each about 20 bases

I got this query to solve for the first 20 but I don’t know how to extend that to the 5 rows,

prepare dna_length(int) as
  with t1 as (
    select chr(65) as s 
      union select chr(67) 
      union select chr(71) 
      union select chr(84) )
, t2 as ( select s, 
            row_number() over() as rn from t1)
, t3 as ( select generate_series(1,$1) as i,
            round(random() * 4 + 0.5) as rn )
, t4 as ( select t2.s 
            from t2 join t3 on (t2.rn=t3.rn))
select 
  array_to_string(array(select s from t4),'') as dna ;