The answer is 20. for x=0,1,2,3,4 and 5 the values of y are 6,8,11,16,17 and 13. These follow the polynomial y=x^5/10-(31/24)*x^4+(65/12)*x^3-(197/24)*x^2+(359/60)*x+6 and for next value of x=6 the value for y=20.

It involves a lot of tedium to solve this type of question and should be discouraged. c++ listing for the proof of the same can be requested.