Prompt User For Integer To Make Sure Length Entered By User Is A Power Of 2

Basically I need to make a program prompts the user for an integer, check to make sure the length entered by the user is a power of 2 and at least 2. Then I need to convert from base e to base 2 then I need to print the tick marks of a ruler based of the value of the length.

I got the whole converting thing working and the check for a power of 2, that wasn't an issue because it didn't require any recursion. I just don't know how to print out the proper tick mark values.

The way it is supposed to work is that it needs to look like this. Say the user enters 8;

012131210
012345678

Or if the user enters 16;

01213121412131210
01234567890123456

The bottom row is pretty much just the index value, that I print fine.

The top row though is supposed to be the length of the ticks on a ruler, with the middle most value being the value of the conversion from base e to base 2 from above. I can get that printed and what I get just looks like this.

For 8;

000030000
012345678

For 16;

00000000400000000
01234567890123456

As you can see I can get the middle value and the index values below but I don't know how to use recursion to get the right numbers.

Here's my current code.

import java.util.*;
public class TickMarks {
public static void main (String args[]){
Scanner input = new Scanner(System.in);
boolean looping = true;
while(looping == true){
System.out.print("Please enter a length: ");

[Code]...

Now the methods isPowerOfTwo() and printLength() both work fine. However, I'm not sure how to get the left and right side working.

My thoughts were to split the length in half and get a left and right side. I gave both of them arrays so I can keep track of the values. Now as you've seen above I get all zeros and I know it's because that's the default value in an array, I just don't know how to get the proper values.