1. The problem statement, all variables and given/known data Hi. I'm trying to solve a serie: Ʃ1∞2n+1*(n+1)! / (n+1)n+1 2. Relevant equations 3. The attempt at a solution I tried solving it with Cauchy's method, but it failed. I also tried using d'alembert criterion, which game me the answer 2, so it should be divergent. However in the solutions it says it's convergent. If anyone could check my solution and see if I did anything wrong or if it's a simple error in the solutions, I'd appreciate!