This function finds the rational generating function of the sequence defined by Fn.

The expression Fn must be a valid closed form expression for a sequence with a rational generating function. The command type(Fn, 'ratseq'(n)) will determine if Fn is a valid expression.

The sequence is assumed to be defined by Fn for all . The optional arguments can be used to specify other information about the sequence.

An optional argument of the form , where c is an integer value, defines the first nonzero term in the sequence to be at index c.

An optional argument of the form , where  are integer indices and  are values of the sequence at those indices.

The command with(genfunc,rgf_encode) allows the use of the abbreviated form of this command.