Fix latex typo

README.md

@@ -49,7 +49,7 @@ Let be $S_n = {\sum}^{n}_{i=1} a_i$ a sequence of partial sums. This repository
 
   $$r^{(n)}\_{k+1} = r^{(n+1)}\_{k} \left( \frac{s^{(n+1)}\_{k}}{s^{(n)}\_{k}} - 1 \right),\ k=1,2,\ldots;\ n=0,1,\ldots$$
 
-  Then, $T_n = S_n - \frac{S_{n+1} - S_{n}}{r^{(n+1)}_{1} - r^{(n)}_{1}} r^{(n)}_{1}$.
+  Then, $`T_n = S_n - \frac{S_{n+1} - S_{n}}{r^{(n+1)}_{1} - r^{(n)}_{1}} r^{(n)}_{1}`$.
 
 ## Installation