Difference between revisions of "2005 OIM Problems/Problem 6"

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== Problem ==
 
== Problem ==
Given a positive integer <math>n</math>, <math>2n</math> points are aligned in a plane as <math>A_1, A_2,\cdots, A_{2n}. Each point is colored blue or red using the following procedure:  In the plane, </math>n<math> circles with end diameters </math>A_i<math> and </math>A_j<math> are drawn, disjoint two by two.  Each </math>A_k<math>, </math>1 \le k \e 2n<math>, belongs to exactly one circle. The dots are colored so that the two points of the same circle have the same color.  Find how many different colorations of the </math>2n<math> points can be obtained by varying the </math>n$
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Given a positive integer <math>n</math>, <math>2n</math> points are aligned in a plane as <math>A_1, A_2,\cdots, A_{2n}</math>. Each point is colored blue or red using the following procedure:  In the plane, <math>n</math> circles with end diameters <math>A_i</math> and <math>A_j</math> are drawn, disjoint two by two.  Each <math>A_k</math>, <math>1 \le k \le 2n</math>, belongs to exactly one circle. The dots are colored so that the two points of the same circle have the same color.  Find how many different colorations of the <math>2n</math> points can be obtained by varying the <math>n</math>
 
circumferences and the distribution of colors.
 
circumferences and the distribution of colors.
  

Revision as of 16:22, 14 December 2023

Problem

Given a positive integer $n$, $2n$ points are aligned in a plane as $A_1, A_2,\cdots, A_{2n}$. Each point is colored blue or red using the following procedure: In the plane, $n$ circles with end diameters $A_i$ and $A_j$ are drawn, disjoint two by two. Each $A_k$, $1 \le k \le 2n$, belongs to exactly one circle. The dots are colored so that the two points of the same circle have the same color. Find how many different colorations of the $2n$ points can be obtained by varying the $n$ circumferences and the distribution of colors.

~translated into English by Tomas Diaz. ~orders@tomasdiaz.com

Solution

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See also

OIM Problems and Solutions