The Whittaker functions WhittakerM(mu, nu, z) and WhittakerW(mu, nu, z) solve the differential equation

They can be defined in terms of the hypergeometric and Kummer functions as follows:

Abramowitz, M., and Stegun I. Handbook of Mathematical Functions. New York: Dover Publications.

Luke, Y. The Special Functions and Their Approximations. Vol 1. Academic Press, 1969.