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Explained about columns
joro
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I think this is false.

Take the first row $A=(1,-1,1,-1,1,0,0)$.

The circulant matrix is: $$ \left(\begin{array}{rrrrrrr} 1 & -1 & 1 & -1 & 1 & 0 & 0 \\ 0 & 1 & -1 & 1 & -1 & 1 & 0 \\ 0 & 0 & 1 & -1 & 1 & -1 & 1 \\ 1 & 0 & 0 & 1 & -1 & 1 & -1 \\ -1 & 1 & 0 & 0 & 1 & -1 & 1 \\ 1 & -1 & 1 & 0 & 0 & 1 & -1 \\ -1 & 1 & -1 & 1 & 0 & 0 & 1 \end{array}\right) $$

The determinant is $1$.

Your definition is with columns, so you may need to transpose.

joro
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