Add comment and formatting

Author: JSorngard

src/check.rs

@@ -51,14 +51,15 @@ pub const fn is_prime(n: u64) -> bool {
         (9_080_190, &[31, 73]),
         (25_326_000, &[2, 3, 5]),
         (4_759_123_140, &[2, 7, 61]),
-        (1_112_004_669_632, &[2, 13, 23, 1662803]),
+        (1_112_004_669_632, &[2, 13, 23, 1_662_803]),
         (2_152_302_898_746, &[2, 3, 5, 7, 11]),
         (3_474_749_660_382, &[2, 3, 5, 7, 11, 13]),
         (341_550_071_728_320, &[2, 3, 5, 7, 11, 13, 17]),
         (3_825_123_056_546_413_050, &[2, 3, 5, 7, 11, 13, 17, 19, 23]),
         (u64::MAX, &[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37]),
     ];
 
+    // Find the smallest basis that is large enough.
     let mut i = 0;
     while WITNESSES[i].0 < n {
         i += 1;