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Go back...The Sage Reference Manual: Graph Theory (available as

PDF
and

HTML)
and
the Sage Reference Manual: Algebraic Numbers and Number Fields (available as

PDF
and

HTML)
give a nice overview of the functionality provided by Sage and, moreover,
and provide tons of excellent exemplaric examples.

The

Homepage of Oriented Matroids
provides all isomorphism classes of oriented matroids for up to $n=8$ elements
and, for non-degenerate, up to $n=9$ elements.
The (non-degenerate) oriented matroids of rank 3 correspond to
(simple) arrangements of great-pseudocircles.
All rank 3 oriented matroids of $n=9$ elements are

realized or classified as non-realizable.

The

Database of Order Types for Small Point Sets
provides realization of all combinatorially different realizable sets of up to $n=10$ points
in the Euclidean plane;
the database for $n=11$ is available on demand.
Note that point sets in the plane correspond to great-circle arrangements
on a sphere with marked north- and south-pole.

Neil J. A. Sloane's talk

``Unsolved Number Theory Sequences from Alekseyev, Meiburg, Resta, van der Poorten, and Pablo Picasso and other OEIS news'' mentioning arrangements of circles, in particular, the sequence

A250001 by Jonathan Wild and Christopher Jones (see also

A288567 and

A288568).
An article about Sloane and the OEIS from

``Quanta Magazine''
that also mentions arrangements of circles,
reprinted by the magazine

``Wired''.

Go back...Last update: May 09 2018 17:52:18.
(c) 2017 Stefan Felsner and Manfred Scheucher