)
                                     * exp(sqrt(-1)*j*k* 2*pi/n)
                    + c.c. + x[0] + (-1)**(j) x[n-1])

    and for n is odd::

        y(j) = 1/n (sum[k=1..(n-1)/2] (x[2*k-1]+sqrt(-1)*x[2*k])
                                     * exp(sqrt(-1)*j*k* 2*pi/n)
                    + c.c. + x[0])

    c.c. denotes complex conjugate of preceding expression.

    For details on input parameters, see `rfft`.

    To process (conjugate-symmetric) frequency-domain data with a complex
    datatype, consider using the newer function `scipy.fft.irfft`.

    Examples
    --------
    >>> from scipy.fftpack import rfft, irfft
    >>> a = [1.0, 2.0, 3.0, 4.0, 5.0]
    >>> irfft(a)
    array([ 2.6       , -3.16405192,  1.24398433, -1.14955713,  1.46962473])
    >>> irfft(rfft(a))
    array([1., 2., 3., 4., 5.])

    N)