Consider the differential equation satisfied by
(1)

where is a Whittaker function, which is given by
(2)

(3)

(Moon and Spencer 1961, p. 153; Zwillinger 1997, p. 128). This is usually rewritten
(4)

The solutions are parabolic cylinder functions.
The equations
(5)

(6)

which arise by separating variables in Laplace's equation in parabolic cylindrical coordinates, are also known as the Weber differential equations. As above, the solutions are known as parabolic cylinder functions.
Zwillinger (1997, p. 127) calls
(7)

the Weber differential equation (Gradshteyn and Ryzhik 2000, p. 989).