Wolfram Cloud Document

u=

b

3

y

+c+a

2

y

;(*{coefficientlist,maxdegree}*)coeffs={CoefficientList[u/y^Exponent[Series[u,y0],y],y],Exponent[u,y]}First[coeffs].(y^Range[Last[coeffs]-Length@First[coeffs]+1,Last[coeffs]])

Out[]=

{{b,0,0,c,0,a},2}

Out[]=

c+

b

3

y

+a

2

y