I came up with it too when I was in school. I was bored and staring at some tiles and noticed that for a square block of tiles with side = n, n^2 = sum(1...n) - sum(1...n-1).
The funny thing is that, since then, I've looked at that formula several times and can't for the life of me figure out I got from the above formula to the the sum of the range formula. I guess younger me was smarter than current me.
The funny thing is that, since then, I've looked at that formula several times and can't for the life of me figure out I got from the above formula to the the sum of the range formula. I guess younger me was smarter than current me.