same problem there. I get manage the mathematic solution who doesn't need to calcul the factorial and who have only one loop to get a sum requested for the solution. All tests are green, but attempt said server time ran out... i can not imagine what can be different to pass the server time obstruction. On my computer, there is no significative delay as long as it is very simple.
In fact, i got an answer show me that my solution was too slow... i do simplification for remove the sum part, but again... too slow.