Timeline for Counting problems where unlabeled is easier than labeled
Current License: CC BY-SA 3.0
7 events
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| Apr 13, 2017 at 12:57 | history | edited | CommunityBot |
replaced http://mathoverflow.net/ with https://mathoverflow.net/
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| Mar 9, 2016 at 2:11 | answer | added | Tony Huynh | timeline score: 4 | |
| Mar 8, 2016 at 14:52 | answer | added | Ira Gessel | timeline score: 5 | |
| Mar 7, 2016 at 3:53 | comment | added | Sam Hopkins | @PerAlexandersson: Perhaps this somewhat trivial example was meant in jest but it actually does fit nicely into the hyperplane arrangement story. You can count unlabeled semiorders by counting regions of $\{x_i-x_j=1\colon 1\leq i,j \leq n\}$ that intersect $x_1 < x_2 < \cdots < x_n$ and you can count unlabeled threshold graphs by counting regions of $\{x_i+x_j = 0\colon 1 \leq i < j \leq n\}$ that intersect $|x_1| < |x_2| < \cdots < |x_n|$. Similarly you can count unlabeled stone arrangements by counting regions of $\{x_i-x_j = 0\}$ that intersect $x_1 < \cdots < x_n$. | |
| Mar 7, 2016 at 2:39 | comment | added | Per Alexandersson | Counting number of ways to put $n$ unlabeled stones in a row is very easy compared to the $n!$ ways to put down the labeled ones... | |
| Mar 6, 2016 at 22:15 | history | edited | Sam Hopkins |
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| Mar 6, 2016 at 22:04 | history | asked | Sam Hopkins | CC BY-SA 3.0 |