n×n grid: every row, column, and diagonal sums to the same magic constant
The Lo Shu square (3×3) is the unique 3×3 magic square. For odd n, the Siamese method constructs a magic square. Dürer's famous 4×4 square appears in his 1514 engraving Melancholia — the bottom row reads 15 14 4 1 (year of completion).