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?
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It seems to be $\displaystyle *\sum_{n=1}^{n}i=\frac{n(n+1)}{2} $ But the thing is like delayed by 1. So $\displaystyle \sum_{n=1}^{n}i+1=\frac{(n+1)(n+2)}{2} $
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