0,1

"Up to direction" means that cycles differing only in starting vertex or direction of traversal are treated as one cycle. a(n) always exists since the wheel graph on n spokes has n cycles.

Jeremy Tan, Table of n, a(n) for n = 0..4890

Andreas Björklund, Determinant Sums for Undirected Hamiltonicity, arXiv preprint arXiv:1008.0541 [cs.DS], 2010.

Erich Friedman, Math Magic (September 2012)

a(3) = 4 since K_4 has 3 Hamiltonian cycles up to direction.

Cf. A244511 (a(n) <= 7), A249906 (records), A305190.

Sequence in context: A266628 A283441 A262219 * A171175 A176053 A259791

Adjacent sequences: A249902 A249903 A249904 * A249906 A249907 A249908

nonn,hard

Jeremy Tan, Nov 08 2014

approved