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Path Complement Graph


PathComplementGraph

The n-path complement graph P^__n is the graph complement of the path graph P_n. The first few are illustrated above.

Since P_4 is self-complementary, P^__4 is isomorphic to P_4. Special cases are summarized in the table below.

P^__n has vertex count n and edge count

 m(P^__n)=(n-1; 2)=1/2(n-2)(n-1),
(1)

where (n; k) is the binomial coefficient.

P^__n is connected for n>=4 and Hamiltonian for n>=5.

P^__n is planar for 1<=n<=6. Its exact graph crossing numbers for n=7, 8, 9, and 10 are 1, 3, 9, and 18, respectively. These values suggest the conjecture

 cr(P^__n)=H(n-2)
(2)

for n>=3, where

 H(m)=1/4|_m/2_||_(m-1)/2_||_(m-2)/2_||_(m-3)/2_|,
(3)

and |_x_| denotes the floor function. The values of H(m) for m=0, 1, ... are 0, 0, 0, 0, 0, 1, 3, 9, 18, 36, 60, 100, ... (OEIS A028723). The conjecture agrees with the exact graph crossing numbers for 3<=n<=10 and matches computed upper bounds to at least n=20 (E. Weisstein, Oct. 1, 2026).

The simplex graph of the path complement graph P^__n is the Fibonacci cube graph F_n (Alikhani and Ghanbari 2024).


See also

Cycle Complement Graph, Graph Complement, House Graph, Path Graph, Tetragonal Antiwedge, Wheel Complement Graph

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References

Alikhani, S. and Ghanbari, N. "Golden Ratio in Graph Theory: A Survey." 9 Jul 2024. https://arxiv.org/abs/2407.15860.House of Graphs. Path Complement Graphs. Empty Graph on 2 Vertices, House Graph (theta 1,2,3), P2 + K1, Path P4, (K3 Box K2) + e, Complement of P7, Complement of , Complement of , Complement of , and Singleton Graph.Sloane, N. J. A. Sequence A028723 in "The On-Line Encyclopedia of Integer Sequences."

Referenced on Wolfram|Alpha

Path Complement Graph

Cite this as:

Weisstein, Eric W. "Path Complement Graph." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/PathComplementGraph.html

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