Function collatz_sequence 

pub fn collatz_sequence(n: u64) -> Option<Vec<u64>>

Returns the full Collatz trajectory from n down to 1.

Returns None when n == 0 or when a checked odd step overflows.

Examples

use use_collatz::collatz_sequence;

assert_eq!(collatz_sequence(6), Some(vec![6, 3, 10, 5, 16, 8, 4, 2, 1]));
assert_eq!(collatz_sequence(0), None);