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

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?

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1 Answer 1

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

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  • $\begingroup$ Oh great observation! I will accept it in a short while. $\endgroup$ Commented Nov 30, 2015 at 14:28

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