# [seqfan] Re: A102421; Start with 2n+1, multiply by 3 and add 1 and divide out any power of 2; ....

William Orrick will.orrick at gmail.com
Tue Aug 25 14:34:14 CEST 2020

```Dear SeqFans,

A122563 as well. That one actually has an incorrect entry that needs to be
fixed too--a(30) should be 0, not 1. The error is presumably due to the
same issue with the Mathematica code that I corrected in A102423.

Best,
Will Orrick

On Sun, Aug 23, 2020 at 8:57 AM David Corneth <davidacorneth at gmail.com>
wrote:

> Hi,
>
> Can I get an extra pair of eyes over at A102421? It seems data was
> inconsistent with a comment even before I got there.
> It describes a function that, well, takes a number and then returns another
> number.
> Like after some magic, 17 becomes 19... according to a comment. But data
> says 17 becomes 19.
> Then 19 becomes 43.
>
> Upon inspection,
> a(8) = a((17 - 1)/2) = 19.
> a(9) = a((19 - 1)/2) = 43
>
> Could that be it?
> There's no reference to (n-1)/2 so that'd be guessing. Or should that be
> read from take 2n+1 in name?
> One could say if x = 2n + 1 then n = (x-1)/2 but to me that doesn't follow
> from the name.
>
> Best,
> David
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/
>

```