Take b = 2.

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

29 is prime.

b^((n-1)/29)-1 mod n = 432, which is a unit, inverse 739.

7 is prime.

b^((n-1)/7)-1 mod n = 800, which is a unit, inverse 1910.

(7 * 29) divides n-1.

(7 * 29)^2 > n.

n is prime by Pocklington's theorem.