+const unsigned function_index_zeta1 =
+ function::register_new(function_options("zeta").
+ eval_func(zeta1_eval).
+ evalf_func(zeta1_evalf).
+ derivative_func(zeta1_deriv).
+ overloaded(2));
+
+//////////
+// Derivatives of Riemann's Zeta-function zeta(0,x)==zeta(x)
+//////////
+
+static ex zeta2_eval(const ex & n, const ex & x)