Number sequence

Jun 06, 2010 11:36

What number is next in this series?
3465
4095
4725
5355
5775
5985
6435

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Comments 6

bohemiancoast June 6 2010, 10:03:38 UTC
Hmm. 6615?

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drplokta June 6 2010, 11:20:08 UTC
Looks like, but I had to Google it.

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bohemiancoast June 6 2010, 13:55:35 UTC
What I mean is, I think it is *quite likely* to be 6615, but that's on the basis of noting a pattern that applies to some but not all of the other numbers.

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nwhyte June 8 2010, 11:01:48 UTC
It is indeed 6615 - odd numbers with 24 factors - what alternative patterns did you think of?

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bohemiancoast June 10 2010, 20:31:23 UTC
Ah, yes, that makes sense. I factored the numbers, but didn't think to count factors. And many of the numbers are of the form

x * 15 * 21 (for 11, 13, 17, 19) though the others aren't...

and 6615 is 21 x 15 x 21 (or 3^3*5*7^2)

I will grant you that this is not a perfect approach. Hence the question mark.

I am now quite surprised that I managed to factor all the numbers without checking the number of factors or considering that the large number of odd factors might be relevant.

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ice_hesitant June 7 2010, 01:39:59 UTC
6435+450+240=7125

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