Return five rows of random DNA instead of just one

This is the code I have to create a string of DNA:

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;

execute dna_length(20);

I am trying to figure out how to re-write this to give a table of 5 rows of strings of DNA of length 20 each, instead of just one row. This is for PostgreSQL.

I tried:

CREATE TABLE dna_table(g int, dna text);
INSERT INTO dna_table (1, execute dna_length(20));

But this does not seem to work. I am an absolute beginner. How to do this properly?