This is my little beginner code and I do not know how to fix it.

```
use rug::{ Integer, Rational };
fn main() {
const N: usize = 20;
let mut c: [Rational; N];
let mut nom : Integer;
let mut denom : Integer;
denom = Integer::from(1);
for k in 1..N+1 {
denom *= Integer::from(2*k*(2*k+1));
let mut num = Rational::from((k, denom));
let mut den = Integer::from(1);
for i in 1..k {
den *= (2 * i * (2 * i + 1)) as u32;
num -= c[k - i - 1] / den;
}
c[k - 1] = num;
println!("{}", num);
}
}
```