2 ms·> Isn't sum(1...n) - sum(1...n-1) just n? Yes. I meant n^2 = sum(1..n-1) + sum(1..n).by nhebb 9y ago> Isn't sum(1...n) - sum(1...n-1) just n? Yes. I meant n^2 = sum(1..n-1) + sum(1..n).