This routine returns the differential operator or differential equation satisfied by the generating function associated to the recurrence. This operator is returned as either a DESol operator or a differential equation (both possibly with initial conditions). No attempt is made to explicitly solve the result.

For the definition of the format of a problem, see the help page for LREtools[REcreate]. The problem can be an RESol structure resulting from a call to LREtools[REcreate].

The output option val can be either DESol which requests operator output (the default) or diff which requests the output in terms of a differential system.

Note: In some cases initial conditions are also needed, so the output=diff result is returned as a set. If no initial conditions are needed, the output is a single ODE.