.— On the Ramsgate Sands

Just six different rings may be formed without breaking the conditions. Here is one way of effecting the arrangements.

A B C D E F G H I J K L M

A C E G I K M B D F H J L

A D G J M C F I L B E H K

A E I M D H L C G K B F J

A F K C H M E J B G L D I

A G M F L E K D J C I B H

Join the ends and you have the six rings.

Lucas devised a simple mechanical method for obtaining the n rings that may be formed under the conditions by 2n+1 children.