And this is what we got when n is equal to four. And we stopped at n equals four because it tells us right over there. We start at n equals one and we go all the way to n equals four. So what does this equal? So let's see, three times one minus one is two, so this is looking good so far. Three times two minus one, that's six minus one, that is five, so still looking good. Three times three minus one, that's nine minus one.