[seqfan] Re: Erase my twins, I'll be back

[Frank Adams-watters]

This property (erasing the first occurrence of each number gives the original 
sequence) is generally known as being a "fractal" sequence. There are quite 
a few of them in the OEIS.

Franklin T. Adams-Watters


-----Original Message-----
From: Christian Lawson-Perfect <christianperfect at gmail.com>
To: Sequence Fanatics Discussion list <seqfan at list.seqfan.eu>
Sent: Wed, Oct 2, 2019 8:26 am
Subject: [seqfan] Re: Erase my twins, I'll be back

That's reminiscent of A003602, which has the property that if you delete
the first occurrence of each positive integer you get the same sequence.

On Wed, 2 Oct 2019 at 13:49, Éric Angelini <eric.angelini at skynet.be> wrote:

> Hello SeqFans,
> erase two successive terms when they are the same.
> The non-erased terms rebuild the starting sequence:
> 1,1,2,2,1,2,2,1,2,1,1,2,1,2,1,1,2,1,2,1,1,2,1,2,1,2,2,1,2,1,2,1,2,
> 2,1,2,1,2,1,2,1,1,2,1,2,1,2,1,2,1,1,2,1,2,1,2,1,2,1,...
> This is easy to build by hand -- and boring: is there a
> simple morphism that could do the job?
> (The "lexicographically first" question is impossible
> to solve here, I guess -- as one can always begin the
> sequence with a bunch of 1s. Or insert a pair of 1s
> at some point to "beat" the previous seq). I just wanted to show this
> example -- a "fractal with an
> eraser" -- which might not enter the OEIS, no problemo!
> Best,
> É.
>
>
> à+
> É.
> Catapulté de mon aPhone
>
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/
>

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