Saw this idea recently. Wondered how susceptible it would be to a brute force approach.

Given a square grid size N, and a list of numbers 2*N**2 2*N, find a fillin (like a crossword), and report the digits in the major diagonal (as an easy proof of solution).

The reference in the spoiler took an hour or two to find the solution. I won't post the solution here, you'll have to do the work yourself.

Quantum Mechanics: The dreams stuff is made of