Next number is (1*n)‎+(sum of all digits)

So first tem is 4.

2nd Term = (1*4)+(0+4)= 8

3rd Term  = (1*8)+(0+8)= 16

4th Term = (1*6)+(1+6) = 13

5th Term = (1*3)+(1+3)= 7

6th Term = (1*7)+(0+7)= 14

7th Term = (1*4)+(1+4)= 9

8th Term = (1*9)+(0+9) = 18