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Number of unlabeled digraphs on n vertices such that every vertex has outdegree 3.
6

%I #17 Nov 08 2019 15:59:01

%S 0,0,0,1,13,1499,257290,56150820,14971125930,4829990898461,

%T 1864386642498918,851204815909786099,454661054439318678263,

%U 281270600132956104641972,199701092658236514672384967,161392692052798327047616107614,147373164027242947672475065773269

%N Number of unlabeled digraphs on n vertices such that every vertex has outdegree 3.

%H Andrew Howroyd, <a href="/A185193/b185193.txt">Table of n, a(n) for n = 1..50</a>

%H L. Travis, <a href="http://arXiv.org/abs/math.CO/9811127">[math/9811127] Graphical Enumeration: A Species-Theoretic Approach</a>

%Y Column k=3 of A329228.

%Y Cf. A001373, A129524, A185194, A185303.

%K nonn

%O 1,5

%A _Nathaniel Johnston_, Feb 08 2012

%E Terms a(10) and beyond from _Andrew Howroyd_, Nov 08 2019