Regarding multiply-armed equiangular (or Logarithmic) spirals

[Rajib & Susmita Bandopadhyay]

Dear friends,
Could you please inform me how could I generate multiply-armed equiangular (or Logarithmic) spirals in Octave(Debian) ?
Since I use Debian Squeeze, I used openofficemath software to generate the formula printed below. The form should be as follows (with summation convention, this is a series):

 with the open office Math format as r_n = a.e^(b*%theta).e^(2 *%pi/n), with graph for every r, i,e, r1, r2, r3,..., rn, plotted separately.
Eagerly awaiting your response.
Regards,
bkpsusmitaa