The magic hexagram
Brian Bolt, Roger B. Eggleton, Joe Gilks · The Mathematical Gazette · 1991
It was at the Fifth Southeast Asian Conference on Mathematical Education (June 1990, in Brunei Darussalam) that Brian Bolt posed the question: Can the numbers 1 to 12 be arranged within the hexagram below to give equal sums in the six indicated directions? This is the Magic Hexagram Problem.