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A129524 Number of unlabeled digraphs on n vertices such that every vertex has outdegree 2. 6
0, 0, 1, 6, 79, 1499, 35317, 967255, 29949217, 1033242585, 39323062014, 1637375262965, 74075329383599, 3619112881630497, 189953824713590782, 10661151595417930874, 637230479685691806302, 40415532825383300892418, 2711124591869919503655096 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 30 22:26 EDT 2020. Contains 337440 sequences. (Running on oeis4.)