param appell4 c array param; array c; appell4 returns the Lauricella function F_C(a,b, c_1, ..., c_n; x_1,...,x_n) for the parameter << param >> = [a, c, b_1, ..., b_n]. In case of n=2, the function is called the Appell function F_4. c = [ generators, variables ] Note that for a special set of parameters, the returned differential equation is not holonomic, e.g., [[1 2 3 4]] appell4 rank :: Example: [ [1 -4 -2 5 6] ] appell4 rank ::