A magic square is a square array of integers in which the numbers in the rows, columns, diagonals add to the same sum.
The illustrated four-by-four magic square occurs in the Passion facade of the Sagrada Familia church in Barcelona, Spain. The magic sum of the square is 33, the age of Jesus at the time of the Passion.
Mathematicians prefer the numbers in their magic squares to be all different. In fact the illustrated square can be converted to such a square by adding 1 to the numbers 10 (left), 11, 14 (right) and 15. The magic square obtained in this way is similar to the famous magic square found in the print ‘Melancholia’ by Albrecht Dürer.
http://en.wikipedia.org/wiki/Magic_square
http://paulscott.info/making/ch25magicF.html
