Answer:
The remainder is 3
Explanation:
1) n^2 - 1 = (n-1)(n+1)
When n^2 -1 is not divisible by 3, it implies that neither (n-1) nor (n+1) is divisible by 3.
From any three consecutive integers, one must be divisible by 3.
The consecutive integers are n, (n-1), (n+1)
n is divisible by 3.
If n is even, the remainder is 0.
If n is odd, the remainder is 3 if divided by 6.
2) n^2-1 is even
n^2 - 1 = even
n^2 = even + 1
n^2 = odd
For 1 + 2 , n is odd.
3,9,15,21,.....
The remainder when n is divided by 6 is odd