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A054958
Number of labeled connected Eulerian digraphs with n nodes and an even number of edges.
2
1, 1, 4, 62, 3512, 664808, 434127872, 1019647584176, 8819902136975232, 284798318582888943488, 34636901578294133264379392, 15970288165992077917879019856128, 28060652850285225214988677642354678784, 188680826646319054103468721801532841166681088
OFFSET
1,3
LINKS
V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.
FORMULA
a(n) = (A054957 + (n-1)!)/2. - Andrew Howroyd, Sep 10 2018
MATHEMATICA
A054957 = Cases[Import["https://oeis.org/A054957/b054957.txt", "Table"], {_, _}][[All, 2]];
a[n_] := (A054957[[n]] + (n - 1)!)/2;
Array[a, 14] (* Jean-François Alcover, Sep 13 2019 *)
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 24 2000
EXTENSIONS
More terms from Vladeta Jovovic, Mar 06 2001
a(12)-a(14) from Andrew Howroyd, Sep 10 2018
STATUS
approved