bash loop: for loop in older bash versions

Question

I have an older version of bash: 3.2.25 I am trying to write a for loop:

#!/bin/bash
filename="K"

for k in {2..20..2}
do
  filename=$filename$k
done

This should give me:

K2
K4
.
.
K20

But this is what it gives me:

K{2..20..2}
K{2..20..2}
.
.
K{2..20..2}

Is it because it is an older version of bash? How can I get it to work? Listing all the values is not a solution because I'm going to have to use {5..201}.

Answer 1

That was added in bash 4, I believe.

You can do:

for (( k=5; k<=201; k+=2 )); do
    filename=$filename$k
done