Use the ratio test to find the radius of convergence of the power series $$1 + 2! x + \frac{4! x^2}{(2!)^2} + \frac{6! x^3}{(3!)^2} + \frac{8! x^4}{(4!)^2} + \frac{10! x^5}{(5!)^2}+\cdots$$

$R =$
(If the radius is infinite, enter Inf for R.)