Graph Problem: (n+1) Knots & Edges - How Many Possible Graphs?

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Discussion Overview

The discussion revolves around a graph problem involving (n+1) knots and the determination of the total number of possible graphs that can be formed without loops. The scope includes combinatorial aspects of graph theory and the enumeration of graph structures.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant presents a problem regarding the number of possible graphs that can be formed with (n+1) knots, specifying that the graphs must not contain loops.
  • Another participant inquires about the number of r-combinations out of n elements without repetition, suggesting a connection to the graph problem.
  • A subsequent post reiterates the inquiry about r-combinations and proposes that the number of combinations is double the number of graphs, indicating that for larger n, the total number of graphs must exceed just the combinations due to the presence of both tree and non-tree structures.
  • A participant shares links to Wikipedia articles on graph theory and graphical enumeration, indicating a desire for further exploration of the topic.
  • One participant expresses satisfaction in having resolved the problem and sees it as an opportunity to revise graph theory.

Areas of Agreement / Disagreement

The discussion does not appear to reach a consensus on the exact number of possible graphs or the relationship between combinations and graph structures, indicating that multiple views and interpretations remain present.

Contextual Notes

Participants have not fully resolved the mathematical steps or assumptions regarding the relationship between combinations and graph structures, leaving some aspects of the problem open to interpretation.

pixel01
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Hello all,

I have got this graph problem. There are (n+1) knots which are numbered as A1, A2...An,An+1. We can connect those knots with lines (edges). The question is : How many possible graphs are there totally?
Notes: A graph can be a tree of any kinds, but muts not contain a loop.

Thanks
 
Last edited:
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EnumaElish said:

Thanks for your ansser.
The number of combinations out of n elements,without repetition is just double the number of graphs of the same type. For n relatively large, we can have graphs without tree, and graphs with tree structure as well, so the final answer must be higher than just the number of combinations out of n elements...
 
Thanks Enuma. I have done it!
Great chance to revise the graph theory.
 

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