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%I #19 Sep 13 2019 08:02:35
%S 0,0,2,56,3488,664688,434127152,1019647579136,8819902136934912,
%T 284798318582888580608,34636901578294133260750592,
%U 15970288165992077917878979939328,28060652850285225214988677641875677184,188680826646319054103468721801532834939660288
%N Number of labeled connected Eulerian digraphs with n nodes and an odd number of edges.
%H V. A. Liskovets, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL3/LISK/Derseq.html">Some easily derivable sequences</a>, J. Integer Sequences, 3 (2000), #00.2.2.
%F a(n) = (A054957(n) - (n-1)!)/2. - _Andrew Howroyd_, Sep 10 2018
%t A054957 = Cases[Import["https://oeis.org/A054957/b054957.txt", "Table"], {_, _}][[All, 2]];
%t a[n_] := (A054957[[n]] - (n - 1)!)/2;
%t Array[a, 14] (* _Jean-François Alcover_, Sep 13 2019 *)
%Y Cf. A058338, A054955, A007080, A054956, A058337, A054958, A054957.
%K nonn,easy
%O 1,3
%A _N. J. A. Sloane_, May 24 2000
%E More terms from _Vladeta Jovovic_, Mar 06 2001
%E a(12)-a(14) from _Andrew Howroyd_, Sep 10 2018