def on_square(integer_number):
    """This function returns the number of grains on a particular square of the chessboard. See README file for how it is calculated."""

    # We ensure that the input number is greater than zero and less than 65
    if integer_number <= 0 or integer_number > 64:
        raise ValueError('Value should be a positive integer between 1 and 64(inclusive)')
    return 2 ** (integer_number - 1)