start = 1583 stop = 1697 Q = [None,] Q.append(1) Q.append(1) for n in range(3,stop+1): Q.append(Q[n-Q[n-1]]+Q[n-Q[n-2]]) sum_Q = 0 for n in range(start, stop+1): sum_Q = sum_Q + Q[n] print(sum_Q)