\operatorname{arccosh} (x) = \frac{i}{2} \pi - i x - \frac{i}{6} x^{3} - \frac{3 i}{40} x^{5} - \frac{5 i}{112} x^{7} - \frac{35 i}{1152} x^{9} - \frac{63 i}{2816} x^{11} - \\ \quad{}\quad{}\frac{231 i}{13312} x^{13} - \frac{143 i}{10240} x^{15} + \operatorname{O} \bigl(x^{16}\bigr)

`&operatorname`(arccosh)(x) = series(1/2*I*Pi-I*x-1/6*I*x^3-3/40*I*x^5-5/112*I*x^7-35/1152*I*x^9-63/2816*I*x^11-231/13312*I*x^13-143/10240*I*x^15+O(x^16),x,16)