Question 89

Complete the following sequence:
5, 72, 412, 2658, __________?

Solution

The series is in the form of $$2na_n+62\left(n-1\right)\ ,\ n>1$$, where $$a_1=5$$

For n = 2, $$a_2=5\times\ 2+62\times\ 1\ =\ 72$$

For n = 3, $$a_3=72\times\ 4+62\times\ 2\ =\ 412$$

For n = 4, $$a_4=412\times\ 6+62\times\ 3=\ 2658$$

For n = 5, $$a_5=2658\times\ 8+62\times\ 4\ =\ 21512$$

Thus the correct option is C.

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Complete the following sequence:5, 72, 412, 2658, __________?