OFFSET
1,2
COMMENTS
For n > 2, the number of minimum vertex colorings of the n-barbell graph.
a(n) is also the number of minimum distinguishing labelings of the (n-1) x (n-1) complete bipartite graph K_n,n. - Eric W. Weisstein, Sep 07 2024
LINKS
Eric Weisstein's World of Mathematics, Barbell Graph.
Eric Weisstein's World of Mathematics, Distinguishing Number.
Eric Weisstein's World of Mathematics, Minimum Vertex Coloring.
MATHEMATICA
Table[(n - 1) n! (n - 1)!, {n, 20}]
Table[(n - 1) n Gamma[n]^2, {n, 20}]
Table[2 Binomial[n, 2] Gamma[n]^2, {n, 20}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Mar 03 2024
STATUS
approved