The poly2sym(M,x) function returns a polynomial with indeterminate x, using the elements of M as coefficients.

$\mathrm{with}\left(\mathrm{MTM}\right)\:$

$M≔\mathrm{Matrix}\left(1\,3\,'\mathrm{fill}'=1\right)\:$

$\mathrm{poly2sym}\left(M\right)$

$x^2+x+1$

$M≔\mathrm{Matrix}\left(\left[\left[1\,2\,3\right]\,\left[4\,5\,6\right]\right]\right)\:$

$\mathrm{poly2sym}\left(M\,'y'\right)$

$y^5+2y^4+3y^3+4y^2+5y+6$