OFFSET
0,2
COMMENTS
A digraph is Hamiltonian if it contains a directed cycle passing through every vertex exactly once.
LINKS
Wikipedia, Hamiltonian path
EXAMPLE
The a(2) = 4 digraph edge-sets:
{12,21}
{11,12,21}
{12,21,22}
{11,12,21,22}
MATHEMATICA
Table[Length[Select[Subsets[Tuples[Range[n], 2]], FindHamiltonianCycle[Graph[Range[n], DirectedEdge@@@#]]!={}&]], {n, 0, 4}] (* Mathematica 8.0+. Warning: Using HamiltonianGraphQ instead of FindHamiltonianCycle returns a(4) = 19200 which is incorrect *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Jun 14 2019
STATUS
approved