updated README.md

README.md

@@ -21,7 +21,7 @@ them using **rotations**, **translations**, and (optionally) **scale**
 transformations in order to minimize the root-mean-squared-distance (RMSD)
 between corresponding points from either point cloud, where RMSD is defined as:
 
-<img src="http://latex.codecogs.com/gif.latex?\large&space;RMSD=\sqrt{\,\frac{1}{n}\,\sum_{n=1}^N\,\,\sum_{i=1}^3 \left|X_{ni}-\left(\sum_{j=1}^3 cR_{ij}x_{nj}+T_i\right)\right|^2}"/>
+<img src="http://latex.codecogs.com/gif.latex?\large&space;RMSD=\sqrt{\,\frac{1}{N}\,\sum_{n=1}^N\,\,\sum_{i=1}^3 \left|X_{ni}-\left(\sum_{j=1}^3 cR_{ij}x_{nj}+T_i\right)\right|^2}"/>
 
 ...where:
 ```