A129524 Number of unlabeled digraphs on n vertices such that every vertex has outdegree 2.

0, 0, 1, 6, 79, 1499, 35317, 967255, 29949217, 1033242585, 39323062014, 1637375262965, 74075329383599, 3619112881630497, 189953824713590782, 10661151595417930874, 637230479685691806302, 40415532825383300892418, 2711124591869919503655096

Offset: 1

Author

Vladeta Jovovic, May 29 2007

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..50
• L. Travis, [math/9811127] Graphical Enumeration: A Species-Theoretic Approach

Crossrefs

Column k=2 of A329228.

Cf. A001373, A185193, A185194, A185303.

Extensions

Terms a(10) and beyond from Andrew Howroyd, Nov 08 2019