Recent content by greg9381

Perfect! So it could be expressed as this: latex.codecogs.com/gif.latex?x%20-%209\sum_{n=1}^{\infty}{\left%20\lfloor%20\frac{x}{10^n}%20\right%20\rfloor}

Yeah that works, I was just wondering if there was a better way to do it.

(I hope this is the right subforum) I'm talking about the series 1, 1, -1, 1, -1, 1, -1... I thought about it for a long time but I have no idea. If that first term were gone it would just be (-1)^(n+1), but...it's there...

Well, I'm not very advanced (AB calc in high school) so I can't completely understand the article, but it seems to be a way to find the digit sum using a computer? To clarify, I'm wondering if it's possible to have a formula that can be done with pencil and paper, not computers.

Any ideas on this? I googled it and got only answers inolving Excel, C++, etc... A formula for finding the digit sum of a 2-digit number, or only a 3-digit number, would also be interesting. I thought I had a start with this: For a 2-digit number xy, the sum of the digits =...