Find the number of integral values of x for which the expression \(\[ \frac {4^n + 15n - 1}{x} \] \)has an integer value for every positive integer n.

I really need help on this. Thanks to anyone who can solve it!

n=1; x=1;d=0;cycle:a = (4^n + 15*n -1) ;if(a% x==0, goto5, goto7);d=d+1;printx;n=1;x++;if(x<30, goto cycle,discard=0;

x takes the following values:1, 2, 3, 6, 9, 18.