Counting Self-intersecting n-gons

[Brendan McKay]

* David Wilson <davidwwilson at comcast.net> [050422 21:21]:
> Define a self-intersecting polygon as a polygon in which any two
> edges may intersect at a single nonvertex point, but no three edges
> may intersect.

Please clarify whether you mean three edges intersecting in a single
point or intersecting pairwise.

Thanks, Brendan.