I've been trying to prove the Rodrigues formula for Neumann's Spherical functions. The Neumann's Spherical functions are: $$N_n(x))=-(-x)^n\left[\frac{1}{x}\frac{d}{dx}\right]^n\frac{\cos{(x)}}{x}$$
As a guide, I followed the derivation of the Rodrigues formula for Legendre's Polynomials (for reference, view http://www.phys.ufl.edu/~fry/6346/legendre.pdf), yet I don't seem to be getting anywhere.