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P43846
Conway's Thrackles
Mon 2023-05-22 06:51:03
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9589b65fd7db9dc2b5598e7fe3a786aeae89ef3b8430fbce773d17a1739caeca.png
143 KiB 876x832
A thrackle is a drawing on the plane consisting of vertices (points) and edges (non-self-intersecting curves) such that:
• every edge ends in two different vertices, but hits no other vertex; and
• every edge intersects each other edge exactly once, either at a vertex or by crossing at an interior point.
Is there a thrackle with more edges than vertices?
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P43848
P49919
P50003
P50083
P43848
honest
Mon 2023-05-22 06:51:54
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P43846
I don't know
P43883
Mon 2023-05-22 12:51:42
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1d811439a23facb634398361c1b34daea55efc128dbdbb0bede8e06200f10915.png
36.7 KiB 1246x332
I don't think so, but there are with as many edges as vertices.
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P43887
P43894
P49975
P49978
P49998
P43894
Mon 2023-05-22 14:33:13
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P43883
How many different such figures exist, for a given number of vertices? I think the first terms are
1 0
2 0
3 1
4 2
5 10, but I may have missed some configurations
I doodled them on paper, but I can't be arsed to redo them on the computer rn
P43887
wtf does that mean?
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P43898
P45360
P50079
P44316
Thu 2023-05-25 04:37:37
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Given Conway's involvement, I wonder if this is related to some sort of game.
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P44320
P44336
P49935
P44336
Thu 2023-05-25 18:05:52
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P44316
Why would it be? Conway worked on many things that were unrelated to any game
P45360
Thu 2023-06-01 23:15:30
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P43894
I'm trying to think of how to generate them in a manner that ensures we have everything. We could try ignoring the intersections first, then deciding which edges we're going to make intersect each other. Is there a way to generate all the graphs with V vertices and E edges that aren't isomorphic to each other? When I try to generate them I get a lot of duplicates due to isomorphic graphs, so I wonder if there's a more efficient way.
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