A219894 Number of directed 2-regular graphs on n nodes without directed 2-cycles.

1, 4, 9, 55, 453, 4357, 47598, 569769, 7371560, 102525991, 1525164223

Offset: 5

Author

N. J. A. Sloane, Nov 30 2012

Keywords

• nonn
• more

Links

• Gunnar Brinkmann, Generating regular directed graphs, Discrete Math., 313 (2012), 1-7.

Crossrefs

Cf. A096368, A219889, A219890, A219891, A219892, A219893, A219895.

Extensions

a(14) and a(15) from Brendan McKay, Mar 12 2019