This puzzle was described by Edouard Lucas at the
end of the 19th century.
Place three quarters and three pennies in a line of seven cells as
shown in the left illustration - quarters on the left, and pennies on
the right. The middle cell is empty.
Now interchange two groups of coins moving quarters to the right and
pennies to the left. The middle cell has to be empty when you finish.
Coins are moved just in a forward direction. This means you have to
move quarters to the right and pennies to the left only. A move
consists of moving a coin on the adjacent vacant cell, or jumping over
an adjacent coin on the vacant cell immediately behind it.