The first letter of each term is moved three steps forward and
the last letter is moved two steps backward to obatin the corresponding letters of the next term.
The numbers follow the sequence x 2 + 1, x 2 + 2, x 2 + 3, x 2 + 4.
So, 10 is wrong and must be replaced by (4 x 2 + 1)  i.e. 9.