return LongMath.binomial(n, k);
      }

      @Override
      public boolean noAddOverflow(int a, int b) {
        try {
          int unused = IntMath.checkedAdd(a, b);
          return true;
        } catch (ArithmeticException e) {
          return false;
        }
      }

      @Override
      public boolean noAddOverflow(long a, long b) {
        try {
          long unused = LongMath.checkedAdd(a, b);