Add binomial to math

src/math.rs

@@ -49,6 +49,14 @@ pub fn factorial(n: u64) -> u64 {
     result
 }
 
+pub fn binomial(n: u64, k: u64) -> u64 {
+    if k > n {
+        0
+    } else {
+        factorial(n) / (factorial(k) * factorial(n - k))
+    }
+}
+
 pub fn get_divisors(n: u64) -> Vec<u64> {
     let mut divisors = HashSet::from([1]);
     let mut potential_divisor = 2;