Carmelo has been commissioned to create a decorative wall for the 21st Annual X Games cons...

Carmelo has been commissioned to create a decorative wall for the 21st Annual X Games consisting of a square array of square tiles in a pattern forming a large X. The following example shows a pattern with 5 rows and 5 columns. If the wall will have a similar pattern with 21 rows and 21 columns, how many of the colored tiles will be needed?