of Vietnam but why this problem became well-known?? Vietnamese
friends, do you know?  The 5th person in the ranklist may know :)

    As a theory , one French mathematician named Lucas once visited
Hanoi , and he was appealed by the scenery of Hanoi Tower . So he
named the game he invented as "Ha noi Tower" ( which was famous
later).
  Nguyen Viet Bang (1985 - oo } :-)