Arrange nine digits in a 3x3 array such that each different digit that appears appears as many times as its cardinality, so for example, if the digit 3 appears at all, it appears 3 times. Also the eight 3-digit numbers formed from the rows, columns (top to bottom) and two diagonals (also top to bottom) must all be different.
Also, the sum of the nine digits used cannot itself be written using the digits you've included in the array.
What is that sum of these nine digits?
A possible solution:
423
442
334 and rotations/reflections
Sum: 29