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%I #27 Apr 04 2023 22:04:23
%S 1,1,1,3,12,90,2162,179098,51110788,48762860958,157117982629089,
%T 1735975636147643118,66687671220840028265672,
%U 9012793558387399546070260538,4328655012123103085159161399497333,7451986601800967792474321528025564017244,46329541711597124247394557123740768918978380463
%N Number of connected loop-free Eulerian digraphs with n nodes.
%C Parallel edges are not allowed, but 2-cycles are allowed. Since these digraphs have an Eulerian circuit, being weakly-connected is the same as being strongly-connected. - _Brendan McKay_, Apr 04 2023
%D F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 219 (but there is an error).
%D Ronald C. Read, email to _N. J. A. Sloane_, 28 August, 2000.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/EulerianGraph.html">Eulerian Graph</a>
%F Inverse Euler transform of A058338. - _Andrew Howroyd_, Apr 12 2020
%Y Cf. A058338.
%K nonn,nice,hard
%O 0,4
%A _N. J. A. Sloane_
%E a(7) (generated graphs with nauty, filtered and counted with Python) by _Pietro Battiston_, Feb 08 2014
%E a(8) and a(9) added and description clarified by _Brendan McKay_, May 05 2019
%E Terms a(10) and beyond from _Andrew Howroyd_, Apr 12 2020
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