Code which solves sequence gets stuck at one million

Question

I need to solve this sequence in C#.

"Implement a GetSumSix method to calculate the following sum 1/1+1⋅2/(1+1/2)+...+1⋅2⋅...⋅n/(1+1/2+...+1/n)1/1+1·2/(1+1/2)+..