Answer :

The pattern is to square the number, then subtract 5, then add 1. And repeat.
1) 3 x 3 =9
2) 9 - 5 = 4
3) 4 + 1 = 5 
4) 5 x 5 =25
5) 25 - 5 = 20
6) 20 + 1 = 21
7) 21 x 21 = 441
8) 441 - 5 = 436 
The answer is 436

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