Tìm n để 4A + 1 = 5n

$$\begin{gathered} \mathrm{A} = 5+5^2+5^3+. . . +5^{2019} \\ \mathrm{Tìm} \mathrm{n} \mathrm{để} 4\mathrm{A} +1 =5\mathrm{n} \end{gathered}$$