The topic is mainly proved by Abel transformation. This series can be written in the form of anbn product. An-an+ 1 = O (1/N 2) is a convergent series, but bn is not clear, so the topic first gives the estimation of the sum of the first n terms of bn, and then directly uses Abel transformation to get the conclusion that the sum of n to n+PaBK is very small when n tends to infinity, thus obtaining convergence.