Take b = 2.

b^(n-1) mod n = 1.

13 is prime. b^((n-1)/13)-1 mod n = 165, which is a unit, inverse 951.

5 is prime. b^((n-1)/5)-1 mod n = 69, which is a unit, inverse 594.

(5 * 13) divides n-1.

(5 * 13)^2 > n.

n is prime by Pocklington's theorem.