Added comments explaining what the module provides. Removed BigUint for being overkill. Removed the use and returning of the variable m. Renamed the names of the test cases to something more logical.

Author: WinterPancake

src/math/tetrahedral_number.rs

@@ -1,9 +1,12 @@
 // Tetrahedral Numbers: Function to the Nth Tetrahedral Number
 // Wikipedia Reference : https://en.wikipedia.org/wiki/Tetrahedral_number
-use num_bigint::BigUint;
-pub fn tetrahedral_number(n: u64) -> BigUint {
-    let m: BigUint = (((n) * (n + 1) * (n + 2)) / 6).into();
-    m
+//
+// This program provides a function to calculate the nth triangular
+// number defined by T_n = 1 + 2 + ... + n = (n(n + 1)(n + 2))/6 =
+// (n + 2) choose 3.
+
+pub fn tetrahedral_number(n: u64) -> u64 {
+   ((n) * (n + 1) * (n + 2)) / 6
 }
 
 #[cfg(test)]
@@ -23,8 +26,11 @@ mod tests {
     }
 
     test_tetrahedral_number! {
-        input_6: (6, BigUint::from(56u32)),
-        input_8: (8, BigUint::from(120u32)),
-        input_34: (34, BigUint::from(7140u32)),
+        input_0: (0, 0),
+        input_1: (1, 1),
+        input_2: (6, 56),
+        input_3: (8, 120),
+        input_4: (11, 286),
+        input_5: (34, 7140),
     }
 }