Formula

• December 3rd 2008, 08:09 PM
Ideasman
Formula
Determine the # of ways to get from (0,0) to (2,2) ..

I found it is 6 because of

(2,0) = 1
(2,1) = 3
(2,2) = 6
(2,3) = 10
(2,4) = 15
(2,5) = 21
(2,6) = 28

etc..

so who can give me a formula to explain this relationship for a general thing?
• December 3rd 2008, 08:11 PM
vincisonfire
It seems to be $*\sum_{n=1}^{n}i=\frac{n(n+1)}{2}$ But the thing is like delayed by 1. So $\sum_{n=1}^{n}i+1=\frac{(n+1)(n+2)}{2}$