1. Find the number.

What will be the 18th term in the following series?
0, 6, 6, 20, 20, 42,...?

Answer: 
342

Explanation: 
The series is of the form
(1*1)- 1
(2*2)+2
(3*3)- 3
(4*4)+ 4
(5*5)- 5
So the 18th term will be 
(18*18)+18=342.