Starting from zero, add the odd sequence and the answer will be a perfect square.

Ex: Starting from 0, we add the first positive odd number, 1. We find the perfect square 1. Now we add the next odd number, 3. And so on.

0 + 1 = 1

1+ 3 = 4

4 + 5 = 9

9 + 7 = 16

16 + 9 = 25

25 + 11 = 36

36 + 13 = 49

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* Submitted by Jorge Pereira Junior