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

1,4

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.

Sequence in context: A156929 A123796 A184553 * A131237 A024082 A132547

Adjacent sequences: A129521 A129522 A129523 * A129525 A129526 A129527

Keyword

nonn

Author

Vladeta Jovovic, May 29 2007

Extensions

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

Status

approved