[seqfan] Re: Wanted: suggestions of new sequences for poster

Georgi Guninski guninski at guninski.com
Sun Nov 25 09:31:50 CET 2012


Here is an idea for plotting sequences in 2d.

Chose a bijection f: N^2 -> N (I experimented with Cantor pairing).
Set the "value" of (x,y) to a( f(x,y) ).
Interpret the "value" as color. If working with grayscale,
smaller is darker. You can map to RGB or HSV.
Probably sequences with small range are better.

I experimented with a(n):  n mod 2, n mod 5, is_prime(n), sigma_0(n)
and in sigma_0(n) got diagonal structure that if true is strange to me.

Here are some examples in sage (can't set legend yet so read the
name).
http://stefan.guninski.com/oeisposter/


Note that the png images might contain compression artifacts
and I might well have screwed the coding/logic...

For other ideas check this mathoverflow post (discussing compression
visual artifacts):
http://mathoverflow.net/questions/77794/ascii-prime-plots-and-prime-rich-quadratic-polynomials

On Sat, Nov 24, 2012 at 06:57:44PM -0500, Neil Sloane wrote:
> Dear Seq Fans, 3 years ago David Applegate and I made
> a poster to celebrate the birth of the OEIS Foundation.
> It contains 25 of my favorite sequences (you can download it
> from the OEIS Foundation web site, http://oeisf.org).
> 
> I would like to make a new poster, to give out at the big
> AMS meeting in San Diego in January. Can people send me
> suggestions of sequences that have been added to
> the OEIS in the past couple of years that would
> be good material for the poster? Naturally sequences that
> have a striking image associated with them are especially welcome.
> 
> Neil
> 
> _______________________________________________
> 
> Seqfan Mailing list - http://list.seqfan.eu/


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