Let's assume that we want to check, if a number n (e.g. 11) is prime.
We calculate L(11) and check if (L(11) – 1) % 11 == 0.
If the expression is False, we know for sure, that n is not prime. If True it is called pseudo prime, i.e. possibly prime.
The first Lucas numbers starting with L(0):
2, 1, 3, 4, 7, 11, 18, 29, 47, 76, 123, 199, 322, 521, 843
L(11)
>>> (199 - 1) % 11
0
Exercise:
Write a function to test if a number n is “not prime” or “pseudo prime”