JEE Mains Model Paper 2

For n = 2 , an = a22 + 1 = 16 + 1 = 17 . Assume that ak = 22k + 1 = 10m + 7 where k > 1 and m is some positive integer
Now, ak+1 = 22k+1 + 1 = (22k)2 + 1
= (10m+6)2 + 1 = 10 (10m2 + 12m +3) + 7
Thus, last digit of an is 7 ∀ n > 1