I have a revision to my previous entry. I can now envisage a way in which the number list for 7 could be 12,41,8,31 after all. The grid of stones represents a digital LED display of course, but I previously discounted the small, in between stones. I thought they were only there to give a clue as to ...

I must query the solution given by the previous contributor On every digital display I posess, and also on the number 38076 printed on puzzle number 2 of this book, the number 7 starts with an upward stroke on the left hand side. This means that the number sequence for 7 is 19, 12, 41, 8, 31 and not...