# Thread: closed formula for tripple sum

1. ## closed formula for tripple sum

Hello, I came across this problem and I wasn't entirely sure on how to do it. Or how I should start doing it anyways, so was seeing if anyone can point me in the right direction and give me some help. Any help is greatly appreciated, thanks!

2. Hello, just checking back to see if I could get some advice from anyone on this, thanks again!

3. Well I was able to go through the triple summation to get ((64)(8)^(n))/21 - ((8)(4)^(n))/3 + ((2)(2)^(n))/3 - 1/21
At this point I don't understand the whole little o notation, my book doesn't even have information on it, and the internet was not making too much sense either. I'm trying to get an understanding of that little example at the bottom of the problem, any ideas? Thanks again