# Stuck on review math problem

Hey everyone, I am stuck on this question:
$$(2^1)(2^2)(2^3)(2^4)...(2^n) = 210$$

What is the value of n?

I'd love to post what I have so far, except that the problem doesn't involve much work, so as soon as I have the first step I'll have the last...and I haven't yet gotten the first (correct) step.

THANKS!!

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$$2^{1+2+3+...+n}$$=210

don't i feel stupid.... :rofl:

I was doing the exact same thing only with the tn = a + (n-1)d formula instead of the Sn = n/2[2a + (n-1)d] formula!!!

Thank you!

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i found an answer which is not an integer!

Diane_
Homework Helper
Leong said:
i found an answer which is not an integer!
Since 210 is not a multiple of 2, that's to be expected.

it is contrary to the method, because 1 + 2+ 3 +.. +n indicates that n must be an integer if want to use the arithmetic sequence formulae.