Here we see ups and downs in the series so there is a chance of 2 separate series
We can have 20 24 30 38 as one series
And 4 64 196 as other series.
Both series occur alternately so next term has to be of the second series.
In first series difference is
24 – 20 = 4
30 – 24 = 6
38 – 30 = 8
So, difference increases by 2
In second series, We see they are squares i.e. 2^{2}, 8^{2}, 14^{2}
8-2 = 6
14-8 = 6
So next number, ? – 14 has to be = 6
So, ? = 14+6 = 20
So next term is 20^{2} = 400

Here we see ups and downs in the series so there is a chance of 2 separate series
We can have 20 24 30 38 as one series
And 4 64 196 as other series.
Both series occur alternately so next term has to be of the second series.
In first series difference is
24 – 20 = 4
30 – 24 = 6
38 – 30 = 8
So, difference increases by 2
In second series, We see they are squares i.e. 2^2, 8^2, 14^2
8-2 = 6
14-8 = 6
So next number, ? – 14 has to be = 6
So, ? = 14+6 = 20
So next term is 20^2 = 400

Rahul says

20,4,24,64,30,196,38,__

Saran Harika says

Here we see ups and downs in the series so there is a chance of 2 separate series

We can have 20 24 30 38 as one series

And 4 64 196 as other series.

Both series occur alternately so next term has to be of the second series.

In first series difference is

24 – 20 = 4

30 – 24 = 6

38 – 30 = 8

So, difference increases by 2

In second series, We see they are squares i.e. 2^2, 8^2, 14^2

8-2 = 6

14-8 = 6

So next number, ? – 14 has to be = 6

So, ? = 14+6 = 20

So next term is 20^2 = 400