A little less, actually. You treat brown sugar the same as table sugar/cane sugar. Try this calculator: http://hbd.org/cgi-bin/recipator/rec...rbonation.html
Be advised that, unlike corn sugar, using brown sugar to prime will affect the flavor of your beer ever so slightly. That said, it should be a beautiful match for a pumpkin beer, so you picked just the right time to run out of corn sugar!
Edit: So obviously I posted at the exact same time as Mr.Average. Woah, freaky how similar our answers were, even down to what order we said what in, eh?