Take b = 5.

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

71 is prime.

b^((n-1)/71)-1 mod n = 5104, which is a unit, inverse 568.

2 is prime.

b^((n-1)/2)-1 mod n = 5111, which is a unit, inverse 2556.

(2^3 * 71) divides n-1.

(2^3 * 71)^2 > n.

n is prime by Pocklington's theorem.