Take b = 2.

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

47 is prime.

b^((n-1)/47)-1 mod n = 6444, which is a unit, inverse 10617.

13 is prime.

b^((n-1)/13)-1 mod n = 16531, which is a unit, inverse 17489.

(13 * 47) divides n-1.

(13 * 47)^2 > n.

n is prime by Pocklington's theorem.