Hi Guido! Try taking the dot product with the corresponding variable powers list:
CoefficientList[1 + 6 x - x^4, x]
gives
{1, 6, 0, 0, -1}
and
{1, 6, 0, 0, -1} . Array[x^(#-1)&, 5]
or
{1, 6, 0, 0, -1} . Table[x^n, {n,0,4}]
1 + 6 x - x^4
back.
