Back in 2011, a magazine offered £15 for anyone who solved this puzzle first. It goes as follows:
I have written down three different 5-digit perfect squares, which between them use five different digits. Each of the five digits is used a different number of times, the five numbers of times being the same as the five digits of the perfect squares. No digit is used its own number of times. If you knew which digit I have used just once you could deduce my three squares with certainty.
What is the sum of my three perfect squares?
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The conditions: "Each of the five digits is used a different number of times, the five numbers of times being the same as the five digits of the perfect squares" indicates that the possible digit integers can only be 1, 2, 3, 4 and 5. Because the sum of the numbers of times the five digits are used is 15 = 3 × 5 digits = 1 + 2 + 3 + 4 + 5. A program as the one below (Python) can be written to find the valid 5-digit perfect squares. And they are 12321, 12544, 13225, 33124, 34225, 35344, 44521, and 52441. By try-and-error (I am no good in writing program), it is found that The three 5-digit perfect squares that meet the condition: "No digit is used its own number of times" are 12321, 33124 and 34225, where digits appear 1, 2, 3, 4, and 5 times are 5, 4, 1, 3 and 2 respectively. The answer is therefore 1 2 3 2 1 + 3 3 1 2 4 + 3 4 2 2 5 = 7 9 6 7 0 .