For each positive integer n, let Mn be the square matrix (nxn) where each diagonal entry is 2018, and every other entry is 1.

Determine the smallest positive integer n (if any) for which the value

of det(Mn) is a perfect square.

(In reply to

re: n = 4 is a square, regardless of by Daniel)

Yikes! - I was doing my determinants wrong - I was making products by wrapping around long diagonals - and that ain't the ways it's done for n>3

Thanks for correcting me. Back to the drawing board.