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Problem of the Week 850

Squarely Sorted

An integer n, such as 1128, is called "sorted" if its digits are in sorted order. Find an integer n such that both n and n2 are sorted. Since small examples abound (1, 2, 3, 4, 5, 6, 12, 13, 15, 16...), the idea is to find as large an integer as you can with this property.


Request for Problems

The problem section of Math Horizons, a journal of the MAA, is on the lookout for good undergraduate problems with solutions. The turnaround time for acceptance to publication is quite brief (much less than any other problem section). Problems should be sent to M.S. Klamkin, Math Dept, Univ. of Alberta, Edmonton, Alberta T6G 2G1, CANADA

© Copyright 1997 Stan Wagon. Reproduced with permission.

The Math Forum

2 October 1998