Take b = 2.

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

193 is prime.

b^((n-1)/193)-1 mod n = 19766568, which is a unit, inverse 14942612.

23 is prime.

b^((n-1)/23)-1 mod n = 25868511, which is a unit, inverse 16542853.

7 is prime.

b^((n-1)/7)-1 mod n = 14510439, which is a unit, inverse 3237157.

(7 * 23 * 193) divides n-1.

(7 * 23 * 193)^2 > n.

n is prime by Pocklington's theorem.