

A231091


Number of distinct (modulo reflection and rotation) unicursal star polygons (not necessarily regular, no edge joins adjacent vertices) that can be formed by connecting the vertices of a regular ngon.


2



0, 0, 0, 0, 1, 1, 5, 27, 175, 1533, 14361, 151575, 1735869, 21594863
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OFFSET

1,7


COMMENTS

For polygons in general see A000939 and A000949, and especially the GolombWelch reference.  N. J. A. Sloane, Nov 21 2013


LINKS

Table of n, a(n) for n=1..14.
Stewart Gordon, The five possible stars for n=7 (SVG file)
Wikipedia, Unicursal hexagram


EXAMPLE

For n=5, only solution is the regular pentagram.
For n=6, only solution is the unicursal hexagram (see Wikipedia link).
For n=7, two regular heptagrams and three irregular forms are possible.


CROSSREFS

Cf. A000939, A000940.
Sequence in context: A091101 A185622 A225309 * A205774 A326094 A232683
Adjacent sequences: A231088 A231089 A231090 * A231092 A231093 A231094


KEYWORD

nonn,nice


AUTHOR

Stewart Gordon, Nov 03 2013


STATUS

approved



