Which data structure is used for implementing recursive

If 16 15 26 69 260 x,

Find 75% of x+ x

The number of terms in the sequence 5, 20, 80, 320,……………., 5120 is:

800     544     416     352     ?      304

If 2.5 3.5 x 30 124 625

Then, x ² - 1 - 2x = ?

398      308      228      158      98      ?

30       32       67       206       ?       4166

If  152,      242,       x ,    332,     404,       314,

then find the value of (2x – 1)?

Find the  wrong term  in the following series:

4, 14, 45, 142, 427, 1292

351      261      181      111      51      ?

What should come in place of the question mark (?) in the following number series?