1 + 2 + 3 + ` 2006 + 2007 + 2008 + 2007 + 2006 + ` + 3 + 2 + 1 =?

1 + 2 + 3 + ` 2006 + 2007 + 2008 + 2007 + 2006 + ` + 3 + 2 + 1 =?

1 + 2 + 3 + ` ` 2006 + 2007 + 2008 + 2006 + ` ` + 3 + 2 + 1 = (1 + 2008) * 2008 / 2 + (2007 + 1) * 2007 / 2 = 2009 * 1004 + 2007 * 1004 = 403264