This is a diameter-5 magic hexagon. Each integer from 1 to 19 appears exactly once, and the sum of the numbers along any column or diagonal is the same. It is easy to prove that 1 and 5 are the only possible magic hexagon diameters, using the numbers from 1 to the hexagon size. The diameter-1 magic hexagon is trivial, and the diameter-5 magic hexagon is essentially unique. (There are 12 variations which arise by rotating and reflecting the hexagon under the action of the dihedral group of order 12).
For information on the history of the magic hexagon visit Eric W. Weisstein's World of Mathematics page.