The sum of the first n odd numbers is always a square | John Graham-Cumming
I was staring at the checked pattern on the back of an airline seat the other day when I suddenly saw that the sum of the first n odd numbers is always a square. For example, 1 1 + 3 = 4 1 + 3 + 5 = 9 1 + 3 + 5 + 7 = 16 And, of course, it occurred to me t...