A308111 Isomorphism classes of Eulerian digraphs with n vertices, allowing loops.

1, 2, 6, 24, 160, 2512, 129816, 22665792, 13056562208, 24953006054144, 160860329639968800, 3555065836569542246400, 273147301191314006316868352, 73832333258502021627712839197696, 70920540648597652305602460997787710080, 244186544390677638132290202415190606165938176, 3036252267734950687777830287721323374283100639476736

Offset: 0

Author

Brendan McKay, May 11 2019

Keywords

• nonn
• hard

Comments

Eulerian means that for every vertex the in-degree equals the out-degree.

Examples

			For n=2 the a(2)=6 solutions are: two non-adjacent vertices with or without loops (3 cases), two vertices with or without loops connected by edges in each direction (3 cases).
		

Links

• Gus Wiseman, Non-isomorphic representatives of the a(3) = 24 Eulerian digraphs with loops.

Crossrefs

For labeled digraphs rather than isomorphism classes see A229865.

For isomorphism classes with loops forbidden see A058338.

Cf. A308128 (connected version of this).

Cf. A000273, A000595, A002416, A002720, A308161.

Formula

Euler transform of A308128.

Extensions

Terms a(10) and beyond from Andrew Howroyd, Apr 12 2020