A007081 Number of labeled Eulerian oriented graphs with n nodes.

1, 1, 3, 15, 219, 7839, 777069, 208836207, 156458382975, 328208016021561, 1946879656265710431, 32834193098697741359313, 1582809785794578499063205301, 218989607557709869788340418432175, 87269441106898007902526099850864517077

Offset: 1

Author

N. J. A. Sloane, Mira Bernstein

Keywords

• nonn
• nice

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• B. D. McKay, Applications of a technique for labeled enumeration, Congress. Numerantium, 40 (1983), 207-221.
• B. D. McKay, The asymptotic numbers of regular tournaments, Eulerian digraphs and Eulerian oriented graphs, Combinatorica 10 (1990), 367-377.

Formula

a(n) = coefficient of [x_1*x_2*...*x_n]^(n-1) in Product_{1<=iSean A. Irvine, Oct 08 2017