A square array of numbers arranged in rows and columns in such a way that all the rows, all the columns, and both diagonals add up to the same total. Often the numbers used are 1, 2,…, n2, where n is the number of rows and columns. The example on the left in the figure is said to be of ancient Chinese origin; that on the right is featured in an engraving by Albrecht Dürer.
http://www.vtaide.com/png/3x3‐E.htm An interactive 3 × 3 magic square.