OFFSET
0,3
COMMENTS
The only disconnected uniquely colorable graphs are the empty graphs on n > 1 nodes.
LINKS
Eric Weisstein's World of Mathematics, Simple Graph.
Eric Weisstein's World of Mathematics, Uniquely Colorable Graph.
FORMULA
a(n) = Sum_{k=1..n} A369227(n,k).
EXAMPLE
n = 1: singleton graph K_1 (1 graph).
n = 2: 2-empty graph, path graph P_2 (2 graphs).
n = 3: 3-empty graph, path graph P_3, triangle graph C_3 = K_3 (3 graphs).
n = 4: 4-empty graph, claw graph K_{1,3}, diamond graph K_{1,1,2} = K_4-e, P_4, square graph C_4, tetrahedral graph K_4 (6 graphs).
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Eric W. Weisstein, Jan 16 2024
STATUS
approved