Update README.md

Author: evilz

README.md

@@ -11,7 +11,7 @@ algorithm and data structure
 | O(lg n)    | Splitting a set of data in half, then splitting the halves in half, etc.   |
 | O(n)       | Traversing a set of data                                                   |
 | O(n lg n)  | Splitting a set of data in half repeatedly and traversing each half        |
-| O(n2)      | Traversing a set of data once for each member of another set of equal size |
+| O(n²)      | Traversing a set of data once for each member of another set of equal size |
 | O(2n)      | Generating all possible subsets of a set of data                           |
 | O(n!)      | Generating all possible permutations of a set of data                      |
 
@@ -24,7 +24,7 @@ Sample :
 | O(lg n)   | 0.000E+00 | 4.000E+00 | 8.000E+00 | 1.200E+01 | 1.600E+01 | 2.000E+01 |
 | O(n)      | 1.000E+00 | 1.600E+01 | 2.560E+02 | 4.096E+03 | 6.554E+04 | 1.049E+06 |
 | O(n lg n) | 0.000E+00 | 6.400E+01 | 2.048E+03 | 4.915E+04 | 1.049E+06 | 2.097E+07 |
-| O(n2)     | 1.000E+00 | 2.560E+02 | 6.554E+04 | 1.678E+07 | 4.295E+09 | 1.100E+12 |
+| O(n²)     | 1.000E+00 | 2.560E+02 | 6.554E+04 | 1.678E+07 | 4.295E+09 | 1.100E+12 |
 | O(2n)     | 2.000E+00 | 6.554E+04 | 1.158E+77 |     —     |     —     |     —     |
 | O(n!)     | 1.000E+00 | 2.092E+13 |     —     |     —     |     —     |     —     |