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