A die is thrown over and over again. Let \(P_n\) denote the probability that, at some point, the sum of the points, taken from the numbers that came out on the top face of the die, from all the rolls made, is \(n\). Prove that for \(n \geq 7\) the equality \(P_n = 1/6 (P_{n-1} + P_{n-2} + \dots + P_{n-6})\) is true.