In[1]:= x[1, 1] = 0; y[1, 1] = -1;
x[1, 2] = 0; y[1, 2] = 1;
x[1, 3] = -3; y[1, 3] = -2;
x[1, 4] = -3; y[1, 4] = 2;
x[1, 5] = -4; y[1, 5] = -5;
x[1, 6] = -4; y[1, 6] = 5;
x[1, 7] = 2; y[1, 7] = -7;
x[1, 8] = 2; y[1, 8] = 7;

x[n_, i_] := -9 x[n - 1, i] - 4 y[n - 1, i] - 14;
y[n_, i_] := -20 x[n - 1, i] - 9 y[n - 1, i] - 28;

Group[i_] := Select[Table[x[k, i], {k, 1, 15}], # > 0 &];
data = Union[Group[1], Group[2], Group[3], Group[4], Group[5],
   Group[6], Group[7], Group[8]];

Sum[data[[i]], {i, 1, 30}]

Out[1]= 5673835352990