Enigma 1439: Ring of powers
20 April 2013
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From New Scientist #2600, 21st April 2007
I have made a number of cards, and have written on them all the nine-digit ninth powers, all the eight-digit eighth powers and so on down to the single-digit first powers. I have arranged these cards to form a ring so that each digit at the right-hand end of one card as seen from the inside of the ring matches that at the left-hand end of its neighbour, going clockwise.
What is the greatest number of digits I can have in the ring?