login
Number of connected loop-free Eulerian digraphs with n nodes.
5

%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