Making a number pattern with a loop

[moessie]

I want to make a number pattern with a loop like this one:
Capture.PNG

I have now only this:
public partial class index : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{


string c = "";
for (int i = 1; i < 10; i++)
{
lbforloop.Items.Add(c + i++ + i.ToString());
c += " ";
}
}
}