def spectralflux_wavelength_to_frequency(flux, wavelength):
    """
    Converts a given spectral flux at a specific wavelength (f_lambda) to the
    spectral flux density at the equivalent frequency (f_nu).

    Parameters
    ----------

    flux : Float.
        The spectral flux density at the wavelength ``wavelength``.

    wavelength : Float.
        The wavelength we're converting at.

    Returns
    ---------

    f_nu : Float.
        The spectral flux density at the ``wavelength`` equivalent frequency.

    Units
    ---------

    ``flux`` units are erg s^-1 A^-1 cm^-2 (where A is Angstroms).
    ``wavelength`` units are A.
    ``f_nu`` units are Janksy (W Hz^-1 m^-2). 
    """

    f_nu = 3.34e4 * pow(wavelength, 2) * flux
  
    return f_nu