Enigma 1584: Trisquare
30 January 2012
Posted by on
From New Scientist #2749, 27th February 2010 [link]
I invite you to place a digit in each of the nine spaces in a 3 × 3 array so that each digit occurs its own number of times (e.g. if 3 occurs it must occur exactly three times). You can then read eight numbers: three across, three down, and two diagonals read from the top down.
What will be the sum of all the digits used if all these numbers are different and the sum cannot be written using digits from the square?