Use the Medjig method without puzzling. This method is known as the LUX method of John Horton Conway. The three letters are three different Medjig tiles. If you draw imaginary lines between the 1, 2, 3 and 4, you get the L (red marked), the U (yellow marked) or the X (blew marked).

First grid is filled with the LUX tiles. Second grid is a 2x2 'blown up' 9x9 magic square.

Take 1x number from first grid and add 4x [number -/- 1] from the same cell of the second grid.

1x number from grid of Medjig tiles LUX

+ 4x [number -/- 1] from 2x2 'blown up' 9x9 magic square

= 18x18 magic square

Use the LUX method to construct magic squares of order is double odd. See 6x6, 10x10, 14x14, 18x18, 22x22, 26x26 en 30x30