Blog Post #70 - Sum of successive squares - what do we observe?

Take a look at the series below - first 20 set of sum of successive squares

1 ^ 2 + 2 ^ 2 = 5
2 ^ 2 + 3 ^ 2 = 13
3 ^ 2 + 4 ^ 2 = 25
4 ^ 2 + 5 ^ 2 = 41
5 ^ 2 + 6 ^ 2 = 61
6 ^ 2 + 7 ^ 2 = 85
7 ^ 2 + 8 ^ 2 = 113
8 ^ 2 + 9 ^ 2 = 145
9 ^ 2 + 10 ^ 2 = 181
10 ^ 2 + 11 ^ 2 = 221
11 ^ 2 + 12 ^ 2 = 265
12 ^ 2 + 13 ^ 2 = 313
13 ^ 2 + 14 ^ 2 = 365
14 ^ 2 + 15 ^ 2 = 421
15 ^ 2 + 16 ^ 2 = 481
16 ^ 2 + 17 ^ 2 = 545
17 ^ 2 + 18 ^ 2 = 613
18 ^ 2 + 19 ^ 2 = 685
19 ^ 2 + 20 ^ 2 = 761
20 ^ 2 + 21 ^ 2 = 841

What all do we observe and are there specific inferences?