Customized FortranForm output

Question

Let's take the following example

V = (-G*Mn)/Sqrt[x^2 + y^2 + z^2 + cn^2];
Vx = D[V, x];
FortranForm[Vx]

The result is (G*Mn*x)/(cn**2 + x**2 + y**2 + z**2)**1.5.

My questions is the following:

1. How can I replace x, y, z with x(1), x(2), x(3) respectively?

2. How can I get rid of the spaces between the plus signs?

Answer 1

V = (-G*Mn)/Sqrt[x^2 + y^2 + z^2 + cn^2];
Vx = D[V, x] /. {x -> x[1], y -> x[2], z -> x[3]};
StringReplace[ToString[Vx, FortranForm], " " -> ""]