[seqfan] The Online RILYBOT Inverse Equation Solver

Robert Munafo mrob27 at gmail.com
Tue May 1 00:56:55 CEST 2012

Hey seqfans,

As NJAS mentioned last week, my RIES program [1] played a part in a
recent strip of the semi mathy-nerdy-netsavvy comic xkcd [2].

After seeing some of the desires expressed by xkcd forum members, I
decided to implement an online server version of RIES at the address:

  http://www.mrob.com/pub/ries/index.html   (or simply mrob.com/ries )

It's a pretty basic service, mainly due to the constraints of the
server. But it's still kind of fun and certainly adequate for a lot of
the recreational maths that the program was intended for, like the
approximations in last Wednesday's xkcd [2].

RIES is a bit off the focus of this list (its a real numbers search
after all, not integer sequences) but I think a few of you might like
it just the same.

I've bashed on it over the weekend, and gotten a fair amount of
traffic from around the world. I think I have it working pretty well
now (and a page design is at least slightly inspired by OEIS). Feel
free to throw a few numbers at ORIES, and let me know what you think.

- Robert

[1] (RIES is a semi-silly acronym for "RILYBOT Inverse Equation
Solver"; the program source code has been online since 2000). If you
give it "1.234321" for example, it will tell you that "x^2-pi = -phi,
corresponding to the approximation Sqrt[Pi-Phi] ~ 1.234321.

[2] xkcd.com/1047/  "Approximations", is full of examples of just the
sort of thing my program is "meant for". Although I and RIES are
mentioned, Randall Munroe and I did not communicate about it
beforehand and it came as a complete surprise to me. Munroe clearly
likes his numbers almost as much as I do. (See for example xkcd's 221,
798, 759, 718, and 715)

  Robert Munafo  --  mrob.com
  Follow me at: gplus.to/mrob - fb.com/mrob27 - twitter.com/mrob_27 -
mrob27.wordpress.com - youtube.com/user/mrob143 - rilybot.blogspot.com

More information about the SeqFan mailing list