code: @Nonnegative
    public static long getSmallFactorial (@Nonnegative final int n)
    {
      ValueEnforcer.isBetweenInclusive (n, "n", PREDEFINED_MIN_INDEX, PREDEFINED_MAX_INDEX);
      return PREDEFINED_FACTORIALS_LONG[n];
    }
docs: Calculate n! whereas n must be in the range of
  {@value #PREDEFINED_MIN_INDEX} to {@link #PREDEFINED_MAX_INDEX}.
  
  @param n
  Input value
  @return The factorial value.