Crack This Sequence

Level pending

5, 19, 57, 131, 253, ...

What is the 9th term of the above sequence?


The answer is 1461.

Hritesh Mourya by Hritesh Mourya , 21, India

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1 solution

Hritesh Mourya
Jun 30, 2016

General Term of the sequence is given by (2r^{3}+3)

Therefore, 9th term is 2 x 9^{3} + 3 = 1461

1 Helpful 0 Interesting 0 Brilliant 0 Confused

One great way of identifying the order of the general term is by taking differences among successive terms unless you obtain a repeating value. Although I couldn't identify the actual formula, I solved it by Brute Force!! I'll share the rough work on fb....

Arkadeep Mukhopadhyay - 4 years, 9 months ago

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