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KP Graph


The graph Cartesian product K_n square P_r of a complete graph K_n and a path graph P_r has been termed a "KP graph" by Knuth (Knuth 2020; Knuth 2024, pp. 20-21), who restricts their parameters to r>1 and n>2. The KP graphs have vertex count, edge count, and (except for r=1 and r=n=2) graph automorphism count

|V(K_n square P_r)|=rn
(1)
|E(K_n square P_r)|=r(n; 2)+(r-1)n
(2)
|Aut(K_n square P_r)|=2n!.
(3)

KP graphs are regular only for n=1 (corresponding to complete graphs) and n=2 (corresponding to 2×r rook graphs).

Special cases are summarized in the table below.

A KP graph K_n square P_r is graceful iff there exists an n×r matrix of distinct integers x_(ij) in the range 0<=x_(ij)<=m for which the differences

 {|x_(ij)-x_(kj)|:1<=i<k<=n,1<=j<=r} union {|x_(ij)-x_(i(j-1))|:1<=i<=n,1<j<=r}
(4)

are themselves distinct (Knuth 2020).

K_n square P_2 (i.e., the 2×n rook graphs) is ungraceful for all n>5 (Knuth 2024, p. 22).


See also

Graph Cartesian Product, KC Graph

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References

Knuth, D. "Coups de grâceful graphs." Unpublished manuscript. 15 Dec 2020. https://cs.stanford.edu/~knuth/papers/coups.pdf.Knuth, D. E. §7.2.2.3 in The Art of Computer Programming, Vol. 4. Pre-Fascicle 7A, Dec. 5, 2024.Petrie, K. E. and Smith, B. M. "Symmetry Breaking in Graceful Graphs." Lecture Notes in Computer Science, 2833, 930-934, 2003.Smith, B. M. and Puget, J.-F. "Constraint Models for Graceful Graphs." Constraints 15, 64-92, 2010.

Referenced on Wolfram|Alpha

KP Graph

Cite this as:

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

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