Magic squares exist for all values of "n", except for order 2. Magic squares can be classified according to their order as odd, doubly even ("n" divisible by four), and singly even ("n" even, but not divisible by four). This classification is based on the fact that entirely different techniques need to be employed to construct these different species of squares. Odd and doubly even magic squares are easy to generate; the construction of singly even magic squares is more difficult but several methods exist, including the LUX method for magic squares (due to John Horton Conway) and the Strachey method for magic squares.