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

5,2

Links

Table of n, a(n) for n=5..15.

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

Crossrefs

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

Sequence in context: A086692 A242036 A069507 * A203464 A360514 A358446

Adjacent sequences: A219891 A219892 A219893 * A219895 A219896 A219897

Keyword

nonn,more

Author

N. J. A. Sloane, Nov 30 2012

Extensions

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

Status

approved