Given number: 2i+1 It is a series of species ai(cx−x0)di - power series. The radius of convergence of a power series can be calculated by the formula: Rd=cx0+limi→∞ai+1ai In this case ai=2i+1 and x0=0 , d=0 , c=1 then 1=i→∞lim(2i+32i+1) Let's take the limit we find