# PRN in range(0,n)
create or replace function prn(n) as trunc(random() * n)::BIGINT;

# Print numbers in range(0,n) as per the task description
create or replace function task(n) as table (
   with recursive cte as (
     select prn(n) as rand, false as stop
     union all
     select
        prn(n) as rand,
        rand = 10 as stop
     from cte
     where stop != true
   ) select rand
     from cte
     where stop = false
);

.print A sample run:
from task(20);
.print A likely shorter one:
from task(11);