OFFSET
0,3
COMMENTS
An acyclic orientation is an assignment of a direction to each edge such that no cycle in the graph is consistently oriented. Stanley showed that the number of acyclic orientations of a graph G is equal to the absolute value of the chromatic polynomial X_G(q) evaluated at q=-1.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..450
Richard P. Stanley, Acyclic Orientations of Graphs, Discrete Mathematics, 5 (1973), pages 171-178, doi:10.1016/0012-365X(73)90108-8
Wikipedia, Turán graph
FORMULA
a(n) ~ n! / (5 * (1 - log(6/5))^(5/2) * 6^n * (log(6/5))^(n+1)). - Vaclav Kotesovec, Feb 18 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jan 13 2016
STATUS
approved