nested For loops

Hey everyone,
I feel like I've asked this question before, and I searched through all my posts and couldnt find it, so I may just be going crazy, and if not I apologize for the redundancy.

So, I'm trying to use nested for loops to created a pyramid of X's,
as in:
......X
....XXX
..XXXXX
XXXXXXX etc...the dots are there to be abe to format the triangle, I don't need them in the program...

and I have the following code, but I have absolutely no idea how to insert the X's and I was looking for a push in the right direction NOT THE ACTUAL CODE...thanks a lot! <Helpless Chap

Code:

//Chapter 3
//Exercise 5

#include <iostream>
using namespace std;

int main()
{
	const char X = 'X';
	const char SPACE = '.';
	unsigned int i;

	for (i = 0; i < 21; i++)
	{
		for (int spaces = 0; spaces < 21; spaces++)
		{
			cout << SPACE;
			if (spaces == 10)
			{
				cout << X;
				//I want to use a for loop to print X to screen
			}
		}
		cout << endl;
	}
	return 0;
}

Assume that you're using a monospace font.

The nth row has (2n-1) Xs, by observation.
The nth row also has N-n preceding spaces, where N is the number of Xs in the last row.

Effectively,

Code:

Given n rows to be printed
for i=1 to i=n
	for j=1 to j=n-i
		print space
	for k=1 to k=2i-1
		print X