Rajasthan Police Constable Model Paper 4

The series is:
2 1 6 1 7 3 0 8 8 6 3 7 1 2 6 3 5 1 7 2 5 7 3
If in the above series, each multiple of 3 is increased by 1, we get:
2 1 7 1 7 4 0 8 8 7 4 7 1 2 7 4 5 1 7 2 5 7 4
Each prime number is reduced by 1, we get:
1 1 6 1 6 4 0 8 8 6 4 6 1 1 6 4 4 1 6 1 4 6 4
We can see, ‘8’ is the only digit that occurs twice.