Enumerating Carmichael numbers

carmichael.rs

#[derive(PartialEq, Copy, Clone)]
enum State {
    Unknown,
    NotPrime,
    NotCarmichael
}

fn main() {
    let mut a = [State::Unknown; 1000000];
    a[0] = State::NotCarmichael;
    a[1] = State::NotCarmichael;
    for i in 2..a.len() {
        match a[i] {
            State::Unknown => {//prime number
                let mut j = 2*i;
                while j < a.len() {
                    if a[j] != State::NotCarmichael {
                        a[j] = if j % (i*i) == 0 || (j-1) % (i-1) != 0 {
                            State::NotCarmichael
                        }
                        else {
                            State::NotPrime
                        }
                    }
                    j += i;
                }
            }
            State::NotPrime => println!("{}", i), //Carmichael number
            State::NotCarmichael => (),
        }
    }
}