3
$\begingroup$

$9, 27, 31, 155, 161, 1127, ?$

I observed that the first term and second term respectively are $3^2$ and $3^3$. But I have no idea about the subsequent terms.
One more observation I did was, the difference in all of these: $$9, +18= 27,+4=31,+124=155,+6=161,+966=1127.$$ We see the after each alternate number, the difference is increasing: $4,6,...$ so next should be $8$, which gives the answer as $1135$. Which is surprisingly correct. But what is the pattern in the middle numbers?

$\endgroup$
14
$\begingroup$

It seems to be x3, +4, x5, +6, x7, +8 and so on

$\endgroup$
  • $\begingroup$ Oh great observation! I will accept it in a short while. $\endgroup$ – Aditya Agarwal Nov 30 '15 at 14:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.