In Note 2590 (Gazette 1956) I gave a very simple method for constructing a ring of 2n 0’s and 1’s in such a way that each set of consecutive n digits formed a unique number in the scale of 2. For instance with n = 4, the cycle 0111101100101000 provides in turn the numbers 0111 = 7, 1111 = 15, 1110 = 14, 1101 = 13, 1011 = 11, 0110 = 6, 1100 = 12, 1001 = 9, 0010 = 2, 0101 = 6, 1010 = 10, 0100 = 4, 1000 = 8, 0000 = 0, 0001 = 1, 0011 = 3.