A049313 Switching classes of tournaments on n nodes.

1, 1, 1, 2, 2, 6, 12, 79, 792, 19576, 886288, 75369960, 11856006240, 3467430423264, 1893448825054528, 1938818712501985736, 3737086626658278741376, 13606268915761294708760704, 93863103860384959101157737728

Offset

1,4

Links

Table of n, a(n) for n=1..19.

L. Babai and P. J. Cameron, Automorphisms and enumeration of switching classes of tournaments, Electron. J. Combin., 7 (2000), no. 1, Research Paper 38, 25 pp.

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

Formula

Same as for switching classes of graphs but summed only over "level" permutations (same power of 2 divides all cycle lengths)

Example

a(4)=2: the "local orders" form one switching class and the class containing a 3-cycle dominating a point the other.

Crossrefs

Cf. A002854.

Sequence in context: A175516 A244656 A159322 * A062954 A049954 A049952

Adjacent sequences: A049310 A049311 A049312 * A049314 A049315 A049316

Keyword

nonn,nice

Author

Peter J. Cameron

Extensions

More terms from Vladeta Jovovic, Mar 01 2000

Status

approved