Take b = 2.

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

41 is prime.

b^((n-1)/41)-1 mod n = 3335, which is a unit, inverse 3026.

7 is prime.

b^((n-1)/7)-1 mod n = 272, which is a unit, inverse 2438.

(7^2 * 41) divides n-1.

(7^2 * 41)^2 > n.

n is prime by Pocklington's theorem.