magic square (thing)

A square matrix of integers such that each row, column and diagonal have the same sum. Usually consecutive integers are used to fill in the square (of course you can start with any number). Famous historical magic squares have additional properties.

Here's a 3x3 example; each sum is 15.

  8 1 6
  3 5 7
  4 9 2

There's an algorithm for generating odd-order magic squares.