A308111 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

COMMENTS

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

LINKS

Table of n, a(n) for n=0..16.

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

FORMULA

Euler transform of A308128.

EXAMPLE

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).

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.

Sequence in context: A012715 A038205 A012361 * A121773 A304996 A012711

Adjacent sequences: A308108 A308109 A308110 * A308112 A308113 A308114

KEYWORD

nonn,hard

AUTHOR

Brendan McKay, May 11 2019

EXTENSIONS

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

STATUS

approved