# [seqfan] Re: A Sequential Puzzle

charliemath at optonline.net charliemath at optonline.net
Mon Mar 26 23:31:22 CEST 2018

```In case any SeqFan is still looking for the answer to The Missing

Section of the Wall St. Journal's Varsity Math Column:

"Tony Murphy
Missing element:

A function interpolating all of the given points is 120*(2^M-1)/M where
M=-3, -2, -1, (0), 1, 2 ... corresponds to 35,45,60,(q),120,180... etc.

For continuity, q has to be the limit as M-->0 of this function, where
of course the formula doesn't work at M=0. This limit is easily
calculated as 120*ln(2), or approx 83.178.

I guess the surprise is that q is not an integer in this case.

The above solution can be derived by looking at M*Given numbers and
fiddling around with the resulting difference equation."

Note how close Tony's answer is to Olivier's (83 1/6) gotten by
interpolation.

On Sat, Mar 24, 2018 at 10:21 AM, charliemath at optonline.net wrote:

> Some SeqFans may already be acquainted with a weekly column  entitled
> Varsity Math, published Saturdays in the Wall St. Journal's Review
> section.
>
>
> The second ot two problems in today's edition is called The Missing
> Element and reads as follows:
>
>
> The open-ended sequence ...35,45, 60, q, 120,180,280, 450, 744,
> 1260,... has an undisclosed element, q.  Find a simple continuous
> function to generate the sequence and compute the surprise answer for
> q.
>
>
> I did a search for any sequence that contains 35 45 60 120 180 280 450
> 744 1260.
> Seqence A103252 contains each value except 744.  No sequence contains
> all 9 values.
>
>
> I'm guessing this sequence, once found, will make its way into OEIS.
>
>
> Enjoy!
>
>
> Charlie Marion
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/
>
```