Tower of Hanoi
The Tower of Hanoi puzzle was invented by the French mathematician Edouard Lucas in 1883. We are given a tower of eight disks (four in the applet below), initially stacked in decreasing size on one of three pegs. The objective is to transfer the entire tower to one of the other pegs (the third one in the applet below), moving only one disk at a time and never a larger one onto a smaller.
The puzzle is isomorphic to an apparently different one.