[seqfan] Re: Rigidity of an okapi

[Neil Sloane]

Sounds like a wonderful idea.  I suppose it was suggested by the great
novel,  L'Elegance du herisson ?

Is there an elegant hedgehog sequence? With a very spiky graph!   Like
this, perhaps:
https://www.nationalgeographic.com/animals/mammals/h/hedgehog/
The closest I could find is A071168, which is rather like a porcupine.

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com



On Fri, Mar 22, 2019 at 9:51 PM Éric Angelini <bk263401 at skynet.be> wrote:

> Hello SeqFans,
> When they want to write a constrained text,
> French oulipians obey sometimes the "Rigidité
> de l'okapi" command -- a whole text where
> consonants and vowels alternate (the okapi
> alternates bright and dark stripes).
>
> This sequence alternates odd and even digits,
> -- and so do the "first additions" when they
> are considered as a sequence.
>
> I need help to correct and extend S (which
> should be the lexicographically first "okapi"
> seq with no duplicated term):
>
> S = 1,29,21,49,23,27,25,45,47,43,2967,63,2947,65,...
>
> "First additions" are:
>
> F = 30,50,70,72,50,52,70,92,90,3010,3030,3010,3012,...
>
> Both S and F have digits following the pattern
> odd/even/odd/even/odd...
>
> I have computed by hand smthg like 35 terms --
> (a nightmare) but I made so many mistake during
> the process that I prefer to send the above start
> only (in hope that those few terms are ok).
>
> A question I cannot answer: will a 3-digit term
> appear at some point?
>
> Another one:
> Is it possible to start an "okapi sequence" with
> a(1) = 2?
> Thank you in advance,
> Best,
> É.
>
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