Graph of Laplace equation


I have solved the following Laplace equation

a0 = (1/Pi) Integrate[Cos[φ]^2 + Sin[φ]^3, {φ, 0, 2 Pi}] an = (1/Pi) Integrate[(Cos[φ]^2 + Sin[φ]^3)*Cos[n*φ], {φ, 0, 2 Pi}] Plot[an, {n, 0, 10}] bn = (1/Pi) Integrate[(Cos[φ]^2 + Sin[φ]^3)*Sin[n*φ], {φ, 0, 2 Pi}] ann = an*Cos[n*φ] bnn = bn*Sin[n*φ] a = Sum[((r/4)^n)*(ann + bnn), {n, 1, Infinity}] f[r_, φ_] := a0/2 + a ParametricPlot3D[{r,φ, f[r, φ]}, {r, 0, 1}, {φ, 0, 2 Pi}] Plot3D[f[r, φ], {r, 0, 1}, {φ, 0, 2 Pi}] 

My problem is that Plot3D and ParametricPlot3D doesn’t work. Any help?