5.25.20  Coefficients of a polynomial defined by its roots : pcoeff pcoef

pcoeff (or pcoef) takes as argument a list of the roots of a polynomial P.
pcoeff (or pcoef) returns a univariate polynomial having these roots, represented as the list of its coefficients by decreasing order.
Input :

Output :

i.e. (x−1)(x−2)(x²)(x−3)=x⁵−6x⁴+11x³−6x².